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

In a large bowl, whisk together the flour, granulated sugar, 3/4 cup cocoa powder, baking powder, baking soda, and salt.

In a separate bowl, beat the eggs. Then stir in the milk, oil, and 2 teaspoons vanilla extract.

Slowly add the egg mixture to the dry ingredients and mix until just combined.

Carefully pour in the boiling water and mix on low speed until well blended. The batter will be thin.

Divide the batter evenly between the prepared cake pans.

Bake for 30-35 minutes, until a toothpick inserted in the center comes out clean. Allow cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Make the frosting: In a large bowl, beat the butter until light and fluffy. Gradually add the confectioners' sugar and cocoa powder, alternating with the milk, until fully incorporated. Stir in 1 teaspoon vanilla.

Place one cake layer on a serving plate or cake stand. Spread half of the frosting evenly over the top. Top with the second cake layer and spread the remaining frosting over the top and sides of the cake.

Decorate the cake with sprinkles or other toppings as desired.