It was incredibly simple. The ingredients are all things most people keep on hand anyway. The instructions are straightforward, so it's pretty hard to mess up. Just a couple of cakes and some mousse. Done.
EXCEPT...I would make one minor change next time. Either a) spread some dark chocolate ganache on each cake layer before topping it with mousse, or b) put it in the freezer for a bit, then cover the whole thing in a layer of dark chocolate ganache. It would be like a giant Reese's peanut butter cup. And it would win at everything, because GIANT REESE'S PEANUT BUTTER CUP CAKE.
Chocolate Cake With Peanut Butter Mousse
adapted slightly from A Beautiful Mess
1 3/4 cup flour
2 cups sugar
3/4 cup cocoa
2 teaspoons baking soda
1 teaspoon baking powder
1 teaspoon sea salt
1 cup buttermilk
1/2 cup vegetable oil
1 teaspoon vanilla extract
1 cup hot water
Preheat oven to 350°. Grease and line two 8 inch round cake pans with parchment paper. Put all the dry ingredients in a large bowl. Whisk to combine. In another bowl, combine buttermilk, oil, eggs, and vanilla. Pour over the dry ingredients and combine. Add hot water; stir until no lumps remain. Pour batter into two round baking pans lined with parchment paper. Bake for 35-38 minutes. Allow to cool for 10-15 minutes before removing from pans. Cool completely.
Peanut Butter Mousse
1 package cream cheese, cold and cut into cubes
1 cup powdered sugar
3/4 cup creamy peanut butter
1 tablespoon pure vanilla extract
3/4 cup whipping cream
In the bowl of an electric mixer fitted with the whisk attachment, mix the cream cheese, icing sugar, peanut butter and vanilla on medium speed until smooth and fluffy, about 3 minutes. Transfer mixture to another bowl (unless you're lucky enough to have another mixer bowl). Wash and dry both bowl and whisk attachment. Fit the mixer with the bowl and whisk again, and whip the cream on medium high speed until firm peaks form (but not clumpy), about 1 minute. Fold whipped cream into peanut butter mixture and cover and chill until ready to use.
Assembly: There's enough mousse to frost the entire thing, but I kinda liked this one with it's sides bare. But definitely throw some ganache up in there if you make it. You could use the same recipe I did for this cake.