FOR THE CAKE:
½ cup warm strongly-brewed coffee (or 3/4 tsp instant coffee dissolved in 1/2 cup warm water)
½ cup buttermilk
1 cup granulated sugar
¼ cup olive oil
1 large egg
1 egg yolk
½ cup dutch-processed cocoa powder
1 teaspoon cornstarch
1 cup all-purpose flour
1 teaspoon baking soda
¾ teaspoon baking powder
¾ teaspoon kosher salt
FOR THE FROSTING:
½ cup heavy cream
½ cup (4oz) semi-sweet chocolate, chopped
¼ cup (2oz) cream cheese (or 1/2 cup butter and no cream cheese)
¼ cup (2oz; 1/2 stick) salted butter (or 1/2 cup cream cheese and no butter)
1¼ cups icing sugar, sifted
¼ cup dutch-processed cocoa powder, sifted
Sprinkles, flaky salt, nuts, or fruit, for serving.
- Preheat the oven to 350F. Line a 9” cake tin with parchment paper and grease with butter to ensure the cake doesn’t stick.
- To a large bowl, add the warm coffee, buttermilk, and sugar, and whisk until combined. Add the olive oil, egg, and yolk and whisk until fully incorporated. Add the cocoa powder, cornstarch, flour, baking soda, baking powder, and salt to a medium bowl, and whisk to remove any lumps. Alternately, place a fine mesh sieve over the large bowl with the wet ingredients, and sift in the dry ingredients. Use a whisk to mix until fully combined. It’s ok if there are a few small lumps.
- Pour the batter into the prepared cake tin and tap the tin on the counter to release any excess air bubbles. Bake for 25 minutes, or until a skewer inserted into the center comes out clean. Flip onto a wire rack to cool.
- While the cake is baking, prepare the chocolate ganache for the frosting by adding the chopped semi-sweet chocolate and the heavy cream to a microwave safe bowl. Heat in the microwave using 30-second increments, stirring in between, until the chocolate has melted into the cream. Chill in the refrigerator for about 20 minutes.
- To make the frosting, use a stand mixer fitted with the whisk attachment or a large bowl and electric beaters. You can do this by hand, but it will require a bit of elbow grease. Add the salted butter, cream cheese, icing sugar, and cacao powder to the bowl. Pulse on low speed to combine the ingredients, using a rubber spatula to scrape the sides of the bowl as needed. Add the cooled chocolate ganache, and mix on high speed until fluffy, about 30 seconds to a minute. If the icing is thinner than you’d like, chill in the fridge to set up.
- When the cake has cooled completely, use an offset spatula to spread the frosting evenly over the top. Finish with sprinkles, flaky salt, nuts, or fruit.
Make Ahead: The cake, without the frosting, can be wrapped in plastic wrap and stored at room temperature for up to 3 days or in the fridge for up to 5 days.