Honestly, does this really need any explanation?
For 1 9", two-layer cake, you'll need:
+ butter, softened, 2 sticks
+ sugar, 3 cups
+ salt, 1 pinch
+ buttermilk, 2 cups
+ 4 eggs
+ baking powder, 2 tablespoons
+ vanilla extract, 2 tablespoons (OR 1-2 vanilla beans)
+ flour, 2 cups
Preheat oven to 350 degrees F; liberally grease two 9" cake pans.
Cream butter, sugar and salt. Whip in eggs, buttermilk and vanilla. Gently mix in flour and baking powder, until just combined. Evenly distribute batter between 2 pans. Bake for 20-25 minutes, or until golden brown and a toothpick inserted in the center comes out clean. Cool completely.
In the meantime, prepare the cocoa frosting. The following recipe is only an approximation, and will leave plenty of extra - just in case. You'll need:
+ powdered sugar, 1 pound
+ cocoa powder, 1/4 cup
+ shortening, approximately 1/2 cup
+ water, 2-4 tablespoons, if necessary
Combine all ingredients until desired flavor and texture are achieved.
If necessary, use a serrated knife to even the tops of the cakes. Place the first layer bottom-down, top-up. (Two frosting tricks? Apply a dab of frosting to the base of the cake stand to secure the cake; place small slips of parchment around the edge of the first layer, to make clean up a bit easier.) Smooth a liberal amount of frosting over the first layer. Place the second layer top-down, bottom-up. Frost the sides and top to desired smoothness. Remove parchment paper. Serve (peonies not required) and enjoy!