Gather your mise en place; get together all of the equipment needed for the recipe and gather your ingredients.

Preheat oven to 350°F.

Measure out dry ingredients for the cake and mix together; flour, baking powder, baking soda, and salt.

Measure chocolate for cake, and separately measure chocolate for icing.

Measure out in separate bowls eggs, sugar, vanilla, mayonnaise, and water.

For the icing, measure out butter (at room temperature), and cut into cubes. Measure icing sugar and vanilla.

Line baking pans with parchment paper, and spray well with nonstick cooking spray.

Heat 3 inches of water in a pot over high heat, and then place a heatproof bowl over top to form a double boiler. Melt chocolate for the cake.

Whisk together the dry ingredients.

In the bowl of a stand mixer, combine eggs, and sugar with vanilla, and mix on high speed until fluffy, about 3 minutes.

On low speed, mix in the melted chocolate and mayonnaise until well combined.

Mix ⅓ of the flour mixture into the batter, alternating with ⅓ of the water. Continue to add dry ingredients and water until well combined.

Pour the batter evenly into the two pans, and bake for 40 minutes, until a toothpick inserted comes out clean.

While the cake is cooking, melt the chocolate for the icing. Let cool until lukewarm stirring as needed to help it cook down.

In the clean bowl of a stand mixer, whisk together the butter with the icing sugar and vanilla at high speed until light and fluffy, about 5 minutes. Slowly add in the melted chocolate and beat until smooth, scraping down the edges of the bowl with a This word has been an eternal struggle amongst Growing Chefs staff. Is it a flipper? Is it a mixer? Is it offset? All I can tell you is that it is a cooking utensil with a wide, flat blade that is not sharp.spatula as needed.

Once the cakes are cooled, ice one cake and place on top of the second cake, and then ice the top and sides of both cakes.