Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large bowl, whisk together sugar, flour, cocoa powder, baking powder, baking soda, and salt.

Add eggs, buttermilk, oil, and vanilla extract to the dry ingredients and beat until well combined.

Carefully stir in hot coffee until the batter is smooth. The batter will be thin, but this is expected.

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

Allow cakes to cool in the pans for 10 minutes, then remove from pans and transfer to wire racks to cool completely.

For the frosting, beat the butter until light and fluffy. Gradually add confectioners' sugar and cocoa powder, then beat in milk until the frosting reaches a spreadable consistency.

Once the cakes are completely cool, spread frosting on the top of one cake layer, place the second layer on top, and frost the top and sides of the cake. Decorate with sprinkles if desired. Don't forget the candle(s)!