For the Dark Chocolate Cake:

• Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, or line the bottoms with parchment paper.

• In a large mixing bowl, sift together the flour, cocoa powder, sugar, baking powder, baking soda, and salt.

• Add the eggs, milk, vegetable oil, and vanilla extract. Mix until just combined.

• Melt the dark chocolate in a double boiler or microwave, then add it to the batter and mix.

• Gradually pour in the boiling water, mixing until smooth.

• Divide the batter between the prepared pans and bake for 30-35 minutes, or until a toothpick inserted comes out clean.

• Cool the cakes in the pans for 10 minutes before transferring to a wire rack to cool completely.

For the Coffee Buttercream:

• Beat the softened butter in a large bowl on medium speed until light and fluffy, about 3-4 minutes.

• Gradually add powdered sugar, one cup at a time, beating well after each addition.

• Stir in brewed coffee, vanilla extract, and salt, beating until smooth.

• If the frosting is too thick, add heavy cream, 1 tablespoon at a time, to reach your desired consistency.

Assembling the Cake:

• Place one cake layer on a serving plate. Spread a generous layer of coffee buttercream on top.

• Add the second cake layer and frost the entire cake with the remaining buttercream.

• Decorate as desired with chocolate shavings, coffee beans, or a dusting of cocoa powder.

• Refrigerate for 30 minutes to set the buttercream.