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Peanut Butter Swirl Brownies

It doesn’t take much to make me happy. A good brownie, for instance. I could eat brownies all day long and be perfectly content.

That said, boring brownies are for the birds. I like my brownies dressed up and ready to party. Whether filled, frosted, layered, or swirled, a brownie can be so much more than just a plain brown square.

Like, for instance, a dense chocolate wedge swirled with sweet peanut butter filling, permeating all the cracks and crevices like a peanut butter earthquake. Indeed, these peanut butter swirl brownies are a sight to be seen. And promptly eaten.

Peanut Butter Swirl Brownies

A word of warning if you decide to be fancy and bake your brownies in a round cake pan – unless you can figure out how to line the sides of said pan with parchment as well as the bottom, they will be tough to remove. Or, should I say, remove in one piece. They wedge themselves into the pan like a kid at Disneyworld, and no amount of coercion will convince them to come out early. I got them out eventually though, kicking and screaming, otherwise these photos might have looked quite a bit different.

As in, angry brownie splatters on the walls different.

Peanut Butter Swirl Brownies

I tried a slightly different brownie recipe than my usual this time, using a cocoa powder, vegetable oil, and boiling water base in place of my usual butter and melted chocolate. While I did love the texture (they’re pretty much spot on what you’d expect from a box brownie mix – both fudgy and chewy), I missed the rich flavor of the butter. Without the peanut butter swirl, I think these brownies may have been deemed a fail, as they were fairly flat and one-dimensional in flavor. Luckily, with these brownies it’s all about the peanut butter, so you wouldn’t really have known the difference if I hadn’t mentioned it. That said, feel free to substitute your own favorite brownie recipe in its place.

Peanut Butter Swirl Brownies

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For Brownie Base:

  • 1/3 cup dark or dutch-processed cocoa powder
  • 1/4 teaspoon baking soda
  • 1/3 cup vegetable oil, divided
  • 1/4 cup boiling water
  • 1 cup granulated sugar
  • 1 egg
  • 2/3 cup all-purpose flour
  • 1/2 teaspoon vanilla extract
  • 1/4 teaspoon salt

For Peanut Butter Swirl:

  • 3 tablespoons unsalted butter, melted
  • 1/2 cup smooth peanut butter
  • 1/3 cup confectioners’ sugar
  • 1/4 teaspoon salt
  • 1/2 teaspoon vanilla extract


  1. Preheat oven to 350 degrees F. Line an 8-by-8-inch square or round baking pan with parchment paper; butter parchment.
  2. In a large bowl, sift together the cocoa powder and baking soda. Add boiling water and half of vegetable oil and stir until mixture forms a thick paste. Mix in the sugar, egg, and remaining oil. Finally, add the flour, vanilla, and salt and fold until flour is just incorporated, taking care not to overmix.
  3. For the peanut butter swirl, combine peanut butter, butter, and vanilla in a bowl and stir until smooth. Add the confectioner’s sugar and salt and stir until smooth.
  4. Pour chocolate batter into prepared pan, then drop dollops of peanut butter filling on top. Use a butter knife to gently swirl the peanut butter into the batter. Since the peanut butter mixture is quite thick this won’t be perfect, just run your knife through it a few times and let it be.
  5. Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean. Transfer to a wire rack to cool to room temperature. For best results, refrigerate brownies a few hours or overnight before serving.

Adapted from All Recipes and Martha Stewart via The Baker Chick.

All images and text © / Love & Olive Oil

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