2cups/ 452g(4 sticks) unsalted butter, at room temperature
3 ¾cups/ 452g(1 pound) powdered sugar, sifted
¼cupheavy cream, at room temperature (plus more as needed)
2teaspoonsvanilla bean paste or vanilla extract, or the scraped seeds from 1 vanilla pod
Pinchfine sea salt
⅓cupblackberry preserves
For chocolate glaze:
3.5ounces/ 100gdark chocolate, finely chopped
¼cupheavy cream
¼cuppowdered sugar, sifted
2-3tablespoonswarm water
Instructions
Preheat oven to 350ºF. Butter and line three 8-inch round baking pans with parchment paper; lightly butter parchment.
In a large mixing bowl, combine the sugar, flour, cocoa, baking soda, baking powder, whisking until thoroughly combined. Add eggs, buttermilk, wine, oil, and vanilla and beat with an electric mixer on medium speed until all dry ingredients are incorporated. Divide evenly among prepared pans.
Bake for 28 to 32 minutes or until a toothpick inserted in the center comes out clean. Remove from oven and place on a wire rack until cool enough to handle. Run a small knife around the edges of each pan, then gently invert onto wire racks. Cakes should come out cleanly. Allow to cool completely. At this point, the cakes can be frozen until ready to use, up to 1 month. Simply wrap each layer individually in a double layer of plastic wrap and then store inside a large zip top bag (I find frozen cakes to be much easier to work with later, and always freeze mine even if I’m finishing the cake the next day).
To prepare frosting, in the bowl of a stand mixer fitted with the paddle attachment, beat butter on medium speed until very pale and creamy, about 8 minutes. Add powdered sugar, a little at a time, mixing well after each addition. Add cream and vanilla extract and beat until light and fluffy, about 6 minutes more. Add more cream or powdered sugar as needed to acheive desired consistency.
To assemble, if necessary, 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 approximately 1/2 cup of buttercream evenly on top. Rather than trying to spread jam on top of the frosting, I found it was easiest to spread the jam on the underside of the next layer, then carefully flip and gently lay it on top of the first layer. Repeat with the second layer and more buttercream and preserves, and top with 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. At this point if you will be coloring the remaining buttercream, add your food coloring to the mixing bowl and beat until color is uniform.
Remove cake from refrigerator and frost with remaining buttercream, reserving some for piping decorative details if desired. You may opt to return cake to the refrigerator for at least 30 minutes, particularly in warm months, as it will make it easier to glaze and slice.
Meanwhile, to prepare the glaze, place chopped chocolate and heavy cream in a double boiler or a heat-proof bowl set over a pot of simmering water. Stir until melted and smooth. Remove from heat and whisk in powdered sugar, stirring until smooth. Add water 1 tablespoon at a time, whisking well after each addition, until the glaze is nice good pouring consistency. Let cool 10 to 15 minutes or until lukewarm (otherwise it will drip too fast). Transfer to a squeeze bottle if desired to make for more easily controlled drips.
Pour or pipe glaze slowly on top of chilled cake, spreading to edges with an offset spatula, allowing the chocolate to drip over the edges. Continue pouring until desired drizzle effect is achieved (you may not use the entire amount). Decorate with fresh blackberries, dusted with gold luster powder or flakes of gold leaf if desired.
Serve right away, or refrigerate until ready to serve (let cake sit at room temperature for 30 minutes before serving). Refrigerate leftovers in an airtight container (or press a piece of parchment/plastic to the cut sides to keep them sealed); it should stay moist for up to 1 week.