Preheat the oven to 350 degrees
Beat the sugar, cocoa powder, and mayonnaise in a bowl (easier with an electric mixer)
Add in the 1 stick of butter and the instant coffee. Continue to beat
Crack an egg in the bowl one at a time, mixing in between
Put the mixer on the lowest setting and gradually add in cake flour, salt, and baking soda.
Once mixed, slowly pour in the buttermilk and vanilla. Beat until everything is smooth. The batter will almost have a whipped cream consistency.
Grease the two round pans with butter and dust with flour. Spread the cake batter in the pans.
Bake for 30 minutes.
While mixing, make the frosting. Mix the powdered sugar, cocoa powder, and salt together.
Beat with butter until butter is fully mixed in.
Slowly pour the coffee in, then add the vanilla flavoring.
Let the frosting sit for a bit in the refrigerator, about 15 minutes.
Once the cakes are completely cooled, spread the frosting on.
Crush the Oreos. Place on the sides, on the top, and if desired, in the middle layer before adding the second round cake on top.
