Black + Blue Buttercake Recipe

Prep

Preheat the oven to 350°F (175°C). Grease and line an 8-inch round cake pan (or two 6-inch pans) with parchment paper; grease the paper.

Dry ingredients

In a medium bowl whisk together the all-purpose flour, black cocoa powder, baking powder, and fine salt until evenly combined. Set aside.

Cream butter and sugar

In a large bowl or stand mixer fitted with the paddle attachment, beat the softened butter and granulated sugar on medium-high speed for 3–4 minutes until light, pale, and fluffy.

Add eggs and flavor

Reduce speed to medium-low. Add the eggs one at a time, beating briefly after each addition until incorporated. Scrape the bowl as needed. Add the vanilla extract and blueberry purée and mix until combined.

Combine wet and dry

With the mixer on low, add one-third of the dry ingredients, then half of the milk-sour cream mixture (whisk the milk and sour cream together before adding). Repeat, ending with the last third of dry ingredients. Mix just until no streaks of flour remain; do not overmix.

Bake

Pour the batter into the prepared pan and smooth the top. Bake 28–35 minutes (for an 8-inch) or 22–28 minutes (for 6-inch) until a toothpick inserted into the center comes out with a few moist crumbs and the top springs back. Rotate halfway through baking if your oven has hot spots.

Cool

Allow the cake to cool in the pan for 10–15 minutes, then run a knife around the edge, invert onto a wire rack, remove parchment, and cool completely before assembling (at least 1 hour).

Make caramel base: In a medium, heavy-bottomed saucepan set over medium heat, add the granulated sugar in an even layer. Without stirring, allow the sugar to melt. After edges start to liquefy, gently swirl the pan occasionally to encourage even melting. If crystals form on the sides, you can brush them down with a wet pastry brush.

When the sugar is a deep amber (watch closely to avoid burning), carefully add the butter (it will bubble vigorously). Stir with a heatproof spatula until the butter is fully melted and incorporated.

Remove from heat and slowly pour in the heavy cream while stirring (mixture will bubble up). Stir until smooth. Stir in the sea salt. Let cool to warm or near room temperature before using. The caramel will thicken as it cools.

Chill equipment: Place the mixing bowl and whip attachment or beaters in the freezer for 10 minutes to chill (optional but helpful).

Whip: Pour the cold heavy cream into the chilled bowl. Add the powdered sugar and vanilla. Whip on medium-high speed until soft peaks form for a light, pillowy texture, about 2–3 minutes. Do not overbeat to the point of graininess. Keep chilled until assembly.

Prepare berries: Rinse and gently pat dry the blueberries and blackberries. If using larger berries, halve them. Reserve a handful for the very top decoration.

Level and slice: If the cake domed, level the top with a serrated knife. For a layered presentation, slice the cake horizontally into two even layers using a long serrated knife or cake leveler.

Layering (if two layers): Place the bottom cake layer on a serving plate. Spread a thin layer (about 2–3 tbs) of salted caramel over the cake, then pipe or spread a layer of Chantilly cream (about 1/3 of the total). Scatter a couple of tablespoons of fresh blueberries across the cream. Top with the second cake layer and gently press to set.

Finish top: Spread a thin crumb coat of Chantilly cream over the top and sides if desired, then a final even layer of cream on top. Drizzle salted caramel sauce over the top, allowing some to drip down the sides. Arrange fresh berries (blueberries and blackberries) decoratively in the center or around the top. Dust lightly with confectioners' sugar if using.

Chill and serve: Chill the assembled cake for at least 20–30 minutes to set the cream and caramel. Slice with a sharp knife dipped in hot water and wiped dry between cuts for neat slices. Serve chilled or at cool room temperature. Leftovers keep refrigerated up to 2 days (cover to protect the airy cream).