Love and Olive Oil

Sweet Potato Layer Cake with Molasses Buttercream

Sweet Potato Cake with Molasses Buttercream

I’ve has this vision of molasses buttercream floating around my head ever since Heather came to town. She brought some delightful espresso macarons to her book signing this past summer, filled with a surprising molasses buttercream.

I haven’t forgotten it.

Sweet Potato Cake with Molasses Buttercream

I first attempted to re-work the bourbon layer cake, intending to use it as a base for this inspired buttercream, and also playing with the recipe as it has never completely satisfied me in terms of consistency. Unfortunately, my modifications, which I thought would help make the cake lighter and fluffier, only made things worse.

With another cake failure settled into the garbage and me not wanting to give up just yet, I still needed a vehicle for my molasses buttercream. So I turned to my faithful stand-by: Sky High: Irresistible Triple-Layer Cakes. In it was a recipe for a delightful sweet potato cake. Seeing as how we’ve been getting a steady 2 pounds of sweet potatoes each week with our CSA and a whopping 10 pounds this past week, I had no shortage of sweet potatoes. It seemed it was meant to be.

Sweet Potato Cake with Molasses Buttercream

While it isn’t the simplest cake to prepare, the extra step of whipping and folding in the egg whites make the cake light, with a delicate crumb that most sweet potato or pumpkin cakes lack. In fact, I may have to try this trick on the aforementioned bourbon cake as it could definitely use some lightening up.

The cake itself has a very light sweet potato flavor and subtle spiced undertones. It’s like a milder version of pumpkin pie, only with sweet potato, and cake instead of custard (ok, so maybe it’s not like pumpkin pie at all). But my intuition that it would be delightful in combination with a sweet and sticky molasses buttercream? Spot on.

Sweet Potato Cake with Molasses Buttercream

I’ve slowly realized, over the years of making cakes and cupcakes, that buttercream has distinct seasons (and I’m talking about straight up American buttercream here, don’t even get me started on the meringues and other varieties). Summer means soupy buttercream, so you better have some shortening handy. Spring and fall are ideal for buttercream-preparation, where the temperature of “room-temperature” is, apparently, perfect. But I never thought I’d have trouble with winter buttercream, even more so than the pesky summer stuff. It definitely requires some more experimentation on my part to figure it out, but I assume that the butter is simply too cold. Even at room temperature it’s still a chilly 65 degrees. My winter buttercream often stays thick, bordering on buttery/greasy in texture (even though the powdered sugar makes it plenty sweet). Adding more milk/cream to lighten it up only works to a certain extent, after which adding more doesn’t change things one bit. Poor, sad, moody buttercream.

Guess you can add American buttercream to the ever-growing list of seemingly-simple things with which I constantly battle (including, but not limited to: chocolate, chocolate ganache, chocolate candy coating, caramel, and pie crust).

Perfectly fluffy or not, luckily, it still makes for a fantastic cake.

Sweet Potato Layer Cake with Molasses Buttercream

Did you make this recipe?


For Cake:
2 large sweet potatoes (about 1 lb)
3 cups cake flour
3 teaspoons baking powder
1 1/2 teaspoons cinnamon
3/4 teaspoon grated nutmeg
1/4 teaspoon ground cloves
1/2 teaspoon salt
5 eggs, separated
2 1/4 cups granulated sugar, divided
1 stick plus 2 tablespoons unsalted butter, room temperature
1 1/2 teaspoons vanilla
1 1/4 cups whole milk

For Frosting:
2 cups (4 sticks) unsalted butter, room temperature
4 cups powdered sugar, sifted
1/4 cup molasses
1/4 cup milk or cream, more or less as needed


Preheat oven to 400 degrees F. Prick sweet potatoes in a few spots with a fork, then place on a foil-lined baking sheet and bake for about 1 hour, or until the potatoes are very soft and beginning to caramelize. Remove from oven cool slightly.

Reduce the oven temperature to 350 degrees F. Butter the bottoms and sides of three 9-inch round cake pans. Line with parchment paper; butter parchment.

When the sweet potatoes are cool enough to handle, peel of the skins and remove any blemishes. Pulse in a food processor until smooth. Measure out 1 cup of puree (discard or reserve the rest for another use).

In a bowl, sift together flour, baking powder, cinnamon, nutmeg, cloves, and salt. Set aside.

In a large metal mixing bowl or the bowl of a stand mixer fitted with the whisk attachment, beat egg whites on medium speed until frothy. Gradually beat in /4 cup of sugar, increase speed to high, and beat until the egg whites form moderately stiff peaks.

In another large mixing bowl, combine sweet potato, butter, vanilla, and remaining 2 cups sugar. Beat on medium-high speed until light and fluffy, about 2 to 3 minutes. Add the egg yolks, one at a time, mixing well after each addition. With the mixer on low speed, add 1/3 of the dry ingredients, followed by 1/2 of the milk. Repeat with another 1/3 dry ingredients, remaining milk, and finally remaining dry ingredients, mixing until just incorporated.

Using a large rubber spatula, fold 1/4 of egg whites into the batter to lighten it. Add the remaining egg white and continue to fold just until incorporated; be sure not to overmix the batter.

Divide batter among prepared cake pans and bake for 25 to 30 minutes or until a toothpick inserted near the center comes out clean. Let cool for 10 minutes, then turn out onto wire racks and cool completely, at least 1 hour.

To prepare frosting, in a large mixing bowl, beat butter on medium-high speed until smooth and fluffy, 2 to 3 minutes. Add powdered sugar, 1/2 cup at a time, mixing well after each addition. Add molasses and beat until incorporated. Depending on the temperature and consistency of your frosting at this point, add milk or cream, 1 tablespoon at a time as needed, then continue beating until frosting is light and fluffy.

To assemble, level each cake layer by cutting of the domed top with a long serrated knife. Place one layer, flat side down, on a cake stand or serving platter. Spread on a layer of buttercream using an offset spatula. Position second layer on top and press to adhere. Repeat with another layer of buttercream, and then position final cake layer, flat side up.

Cover the entire cake with a thin layer of buttercream. This “crumb coat” will make frosting the cake easier. Refrigerate for about 15 minutes to allow this crumb coat to set.

Remove cake from refrigerator and frost with remaining buttercream, reserving some for piping decorative details if desired.

Cake base adapted from Sky High: Irresistible Triple-Layer Cakes.

All images and text © / Love & Olive Oil

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  1. Hi, this cake looks amazing! Any ideas on veganising it for my brother?! 

  2. I’ve made this cake many many times. It’s amazing.

  3. This looks delicious!! Do you know if it would work with oat or almond milk instead of the whole milk?

  4. Nope. I am a good baker. Something must be amiss with the recipe as written. I thought it very odd to have all that baking powder in a cake and no soda. It was dense. Not light at all. I’m familiar with the process and folding in egg whites etc. Have made scratch German Chocolate many times. Followed the directions exactly. A lot of time invested to take to an event (My mistake taking something I had not made before. Won’t do that again.)

    • Sorry your cake didn’t turn out. By nature a sweet potato cake is going to be denser than, say, a plain yellow cake if that’s what you are comparing it to, but in my experience it was still delicious. A number of others have made it without issue as well. There are a number of reasons why a cake might turn out too dense. Was it maybe underbaked? Or could your baking powder have been expired, perhaps?

  5. I made this cake, with a brown sugar cream cheese frosting, and won Best In Show for my state fair!! Thank you Love and Olive Oil! Janet

  6. Making the cake exactly how you made it, how much leftover frosting is there? 
    I hate when there’s leftover frosting and when recipes don’t give you a heads up lol.. please response ASAP, it’s in the oven now!

    • It really depends on your frosting technique, how thickly you frost it. Just slather on a super thick layer and you won’t have any leftover. :)

  7. I first made this cake about three years ago and it has been a fall staple for me ever since! It’s full of flavor and not overly sweet, and folding in beaten egg whites gives it a fluffiness you just don’t find in similar vegetable-based cakes.
    I have made two main changes to the recipe.
    First, to cut an hour off the prep time, I use canned yams. Do NOT use candied yams, just canned yams. Try to find them in the lightest syrup possible, and rinse them before use. I’ve found that it doesn’t significantly change the taste, but it does significantly change how long it takes to make the cake.
    Second, the recipe says to beat the egg whites before mixing the other ingredients. If you are faster/less easily distracted than I am, that’s fine. I, however, prefer to mix everything else and beat the egg whites last. That way I don’t risk losing air out of the egg whites before I fold them into the batter.
    On the whole, this is a fantastic recipe that always gets very positive reviews. It will probably be part of my baking repertoire forever. Thanks!

    • Thanks for sharing, I am so glad you love this recipe as much as I do! And yes, using canned yams or canned sweet potato puree is a easy way to speed up the process. :)

  8. Would it be possible to adapt to cupcakes?

  9. i discovered this recipe over two years ago and have made it three times since. This is one hell of a cake. Truly decadent in the nicest of ways, a revival of homespun flavor, a renaissance of richer fall hues that truly satisfy the palate. I made this for coworkers the first time I prepared it, and it was a knockout. Second time for family and they raved as they patted their too-full bellies.  I’ve also adopted your molasses buttercream as THE frosting of choice, no matter the cake or cupcake. For my son’s 2nd birthday, I made yellow cupcakes with the molasses buttercream. I prepped subtle Mickey Mouse face/ear shapes out of melted milk chocolate and placed one atop each mound of molasses buttercream. Parents were in love, and the children were smitten. Thank you for this truly unique recipe that I’ve come to rely upon. I’ve added it to my collection of recipes to pass down to my son. How special to share mama’s modern finds on Pinterest in 50 years when my son is nostalgic for a taste of home. 

  10. hi i just wanted to let you know that ive been thinking about making this cake for probably two months! i JUST got all the ingredients, except the sweet potatoes, about a month ago. whats stopping me from making it, then? the sprinkles! i know i can decorate it any way i want, but i want it to try to look as close to the real thing as possible (its just so pretty!!, can you blame me?) lol.
    so question is, where did you get your sprinkles from? ive been to Giant, Weis, (local grocery stores), target, AND walmart (even though that doesnt say much. i happen to live close to the worst most ghetto walmart ive ever been to that also happens to have a poor selection of everything.). so yah. your answer would be GREATLY appreciated! <3

    • These sprinkles came from Trader Joe’s a few years back… and not something they carry anymore unfortunately.

      HOWEVER I have seen things called ‘crispy pearls’ that are basically little pearls of crispy chocolate. They come in both white and dark, I believe. A quick google search brings up a number of sources! They may be a bit bigger than the sprinkles I used but I think they’d have the same effect.

      Good luck!!

  11. I just bought the ingredients for this to make on thanksgiving. I haven’t been able to stop thinking about this cake. I have never really found much interest in bakimg , but I am totally excited for this try…maybe it will change my mind.

  12. Is there any way to make this dairy-free? 
    I hate doing all the substitutions, but this sounds SO YUMMY that I REALLY want some and my (nursing) daughter is allergic to milk. :( 

  13. Do you think substituting boiled apple cider would work in place of the molasses?

    • You mean like boiled down until it was thick and syrupy? I think so, as the molasses is mainly a flavoring agent in the frosting. As long as the consistency of the boiled cider was comparable to molasses, if you preferred the flavor of it I think it would work fine. If it is thinner though just be careful not to add too much or it might affect the consistency of the frosting.

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