• Preheat your oven to 350F.
• Take three 8 inch round cake pans and butter them. Then, line with parchment and finish by dusting with a little bit of cocoa, tapping out the excess.
• In a stand mixer with a paddle attachment, add the softened butter, light brown sugar, and vanilla and beat on medium-high speed until the color lightens and the volume increases. About 5-7 minutes. Decrease the speed to medium and add the eggs individually, while beating to incorporate each into the sugar mixture.
• Next sift the flour, cocoa, baking soda, and baking powder into a medium bowl. Add the salt to the dry mix and whisk quickly to stir.
• While setting the mixer on medium speed, alternately mix in the buttermilk and dry mix, until just incorporated.
• Gently fold in the mayonnaise with a whisk and combine until just blended.
• Pour the batter evenly between the 3 cake pans. Smooth the surface with an offset palette knife and bake for 20 minutes, rotate, and then finish baking for another 10 minutes. To test, stick a toothpick into the center and pull out- there should be a few sticky crumbs attached.
• Let cool for 20 minutes on a wire rack and then carefully invert the cake to an additional rack. Gently peel off the parchment paper and let cool completely.

To Assemble

• Trim any doming or rough edges from the cakes with a sharp serrated knife. Wrap in a layer of plastic wrap and place into the freezer to firm up for about 15 minutes (does wonders for assembly!).
• Take a 8 inch cardboard cake round and spread a thin layer of icing with an offset palette knife. Place the first layer of cake on the board, face up.
• Using the palette knife again, spread about 1 cup of chocolate icing on top, leaving 1 inch empty around the edge of the cake. Place the second layer on, face up.
• Repeat using the vanilla buttercream.
• Place the final cake layer on, face down, and top with the strawberry buttercream, leaving a 1 inch gap around the edges of the cake.
• Fill 3 piping bags with a tip of your choice (I used a large star) and decorate the edges as you choose, filling in the gaps as you go.
• Top with fresh fruit, jimmies, sprinkles, maraschino cherries, or crumbled chocolate waffle cone.