Chocolate-Covered Marble Cake with Chocolate Buttercream

Instructions

For the Cake:

1. Line an 8-inch (20cm) square baking pan with parchment paper and set aside.
2. Preheat the oven to 350°F (180°C) for about 5 minutes before baking the cake.
3. Sift the flour, baking powder, and salt into a bowl, mix well, and set aside.
4. Combine the white chocolate and butter in a large bowl and microwave in 30-second intervals, stirring until completely melted. Let it cool at room temperature for a few minutes.
5. Add the sugar, eggs, and vanilla, and mix well with a wire whisk until well combined.
6. Gently fold the dry ingredients in two additions, alternating with the milk, until smooth. Do not overmix the batter.
7. Separate about 1 cup of batter into another bowl and add the cocoa powder (sifted). Gently mix with the wire whisk until smooth.
8. Pour the white batter into the prepared pan and place several dollops of chocolate batter on top. Using a small knife, swirl throughout the batter to create a marbled pattern.
9. Bake for about 25 minutes or until a toothpick inserted into the center of the cake comes out clean.
10. Allow to cool completely at room temperature.

For the Chocolate Buttercream Filling:

1. Combine butter, powdered sugar, cocoa powder, vanilla, and milk in the bowl of an electric mixer. Quickly stir with a spatula and then beat on medium speed until well combined and smooth.
2. Add the melted chocolate and beat until combined. Make sure the chocolate isn't hot to avoid melting the butter.
3. If needed, chill the filling until it reaches a good spreading consistency.
4. Level the top of the cake (optional) and slice it into two layers.
5. Place the first cake layer on the serving plate and spread the filling. Position the second cake layer on top and spread a thin layer of filling all over the cake to catch any loose crumbs.
6. Refrigerate for about 20 minutes.

For the Chocolate Topping:

1. Melt the chocolate in the microwave in 30-second intervals, stirring until smooth.
2. Add 2 tablespoons of milk and mix with a spatula. If the mixture gets too thick, gradually add more milk, stirring until it forms a smooth and fluid mixture. The amount of milk may vary depending on the type of chocolate, as dark chocolate may require a little more milk.
3. Stir in the chopped nuts until well combined.
4. Place strips of parchment paper under the four sides of the cake to keep the serving plate clean.
5. Cover the cake with the chocolate topping and remove the parchment paper strips.
6. Refrigerate for about 20 minutes to set the chocolate.