Step 1: Preheat the Oven

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

Step 2: Make the Cake Batter

1. Cream Butter and Sugar: In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
2. Add Eggs and Vanilla: Beat in the eggs one at a time, then add the vanilla extract, mixing until well combined.
3. Combine Dry Ingredients: In another bowl, whisk together the flour, baking powder, and salt.
4. Mix Dry and Wet Ingredients: Gradually add the dry ingredients to the wet mixture, alternating with the milk. Begin and end with the dry ingredients, mixing until just combined.

Step 3: Bake the Cake

1. Divide Batter: Pour the batter evenly into the prepared cake pans.
2. Bake: Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
3. Cool: Allow the cakes to cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

Step 4: Make the Frostings

1. Chocolate Frosting: In a medium bowl, beat together the cocoa powder, softened butter, powdered sugar, milk, and vanilla extract until smooth and creamy.
2. Vanilla Frosting: In another bowl, beat together the softened butter, powdered sugar, milk, and vanilla extract until smooth and creamy.

Step 5: Assemble the Cake

1. Layer the Cakes: Once the cakes are completely cool, place one layer on a serving plate. Spread a layer of chocolate frosting on top.
2. Add Second Layer: Place the second cake layer on top and frost the top and sides with the vanilla frosting. Use a spatula to create a smooth finish or decorative swirls.

Step 6: Serve

1. Garnish: Optionally, you can decorate the top with chocolate shavings, sprinkles, or fresh fruit.
2. Slice and Enjoy: Slice the cake and serve it to your guests.