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

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In another bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the wet mixture, alternating with the milk. Mix until just combined.

Divide the batter evenly between the prepared cake pans.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool in the pans for 10 minutes, then turn them out onto wire racks to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Add the cocoa powder and mix until well combined.

Gradually add the powdered sugar and milk, alternating between the two, until the frosting reaches the desired consistency.

Stir in the vanilla extract.

Once the cakes are completely cooled, place one layer on a serving plate.

Spread a layer of chocolate frosting on top of the first cake layer.

Place the second layer on top and frost the top and sides of the cake with the remaining chocolate frosting.

Slice and serve as desired.