FOUR-LAYER CHOCOLATE BIRTHDAY CAKE WITH MILK CHOCOLATE GANACHE AND NUTELLA BUTTERCREAM

Steps:

• Preheat oven to 350˚. Butter two 9"-diameter cake pans and line bottoms with parchment paper rounds. Butter parchment and dust with flour, tapping out excess.
• Heat chocolate, coffee, and ⅔ cup cocoa powder in a medium heatproof bowl set over a medium saucepan of barely simmering water (water should not touch bottom of bowl), stirring until chocolate melts and mixture is smooth. Let cool, then whisk eggs, buttermilk, and vanilla into chocolate mixture.
• Using an electric mixer on low speed, mix salt, baking powder, baking soda, and 2 cups flour in a large bowl just to combine. Add brown sugar, oil, ½ cup butter, and ½ cup reserved chocolate mixture and beat on medium speed until flour is evenly distributed and mixture is smooth, about 2 minutes. Add remaining chocolate mixture in 2 additions, scraping down sides and bottom of bowl as needed and beating until smooth after each addition. Scrape batter into prepared pan and smooth top.
• Bake cake until top is firm to the touch and a tester inserted into the center comes out clean, 30-40 minutes. Transfer cake pan to a wire rack and let cake cool in pan 10 minutes before turning out onto a wire rack. Let cool completely.
• Using a serrated knife and moving it back and forth in long, even strokes, carefully halve cakes lengthwise.
• Place 1 cake layer, cut side up, on a platter. Using a rubber spatula, spread one-third of ganache over cake, spreading to edges. Place another cake layer, cut side down, on top and spread another third of ganache over cake. Repeat process once more with another cake layer and remaining ganache; top with remaining cake layer (leave top bare). Chill cake 1-8 hour.
• Spread buttercream all over top and sides of chilled cake, making decorative swirls and swooshes. Decorate with sprinkles, if desired.