1 1/2 cups butter
6 ounces unsweetened baker’s chocolate, chopped
3 cups granulated sugar
5 large eggs
1 1/2 teaspoons vanilla extract
1 1/2 cups all-purpose flour
3/4 teaspoon salt
1/2 tsp. baking soda
In a medium saucepan over medium-low heat, melt butter and chocolate; stir until smooth. Transfer to a large bowl and whisk in sugar. Add eggs, one at a time, whisking well after each addition. Whisk in vanilla, flour, salt and baking soda.
Pour into three greased and floured 9-inch round baking pans. Bake at 350° for 23-25 minutes. Cool for 10 minutes; remove from pan to a wire rack to cool completely. Wrap in plastic wrap or store in air-tight containers until needed.
Peanut butter layers:
6 cups powdered sugar
2 cups creamy peanut butter
1/2 cup butter, melted
1/4 cup (maybe more) heavy cream
Mix together the powdered sugar, peanut butter and melted butter in a standing mixer fitted with the paddle attachment. Mixture will be crumbly. Add cream 1 tablespoon at a time until the mixture becomes a consistent workable dough. It should not be crumbly or stick to your fingers. The mixture should hold together easily when a small amount is squeezed tight in the palm of your hand.
Divide the dough into two even portions. Spray one (or two if you have them) 9-inch spring-form pans with cooking spray or line two 9-inch pans with parchment rounds. Press peanut butter dough into the bottom of the pans evenly, forming the peanut butter layers. Turn the layers out onto two cookie sheets and place in freezer until frozen solid.
Chocolate frosting:
1 1/2 cups butter, softened
1 1/4 cups powdered sugar
1/2 cup unsweetened cocoa powder
2 tsp. vanilla extract
1 tsp. espresso powder
Beat softened butter and powdered sugar together in the bowl of a standing mixer fitted with the whisk attachment. Scrape down the sides of the bowl and beat again until creamy. Add cocoa powder and vanilla extract; beat well. Add espresso powder and beat for 1-2 minutes longer until thoroughly incorporated.
(Note: I use King Arthur espresso powder, but you could substitute finely ground instant coffee)
Assembly:
8 peanut butter cups, each cut in half
3 tsp. chocolate shavings
Pearlized gold crystal sugar *optional
Remove peanut butter layers from the freezer. Thinly frost a brownie layer and top with a peanut butter layer; frost peanut butter layer and top with a brownie layer. Repeat steps until all layers are frosted and stacked. Thinly frost the entire cake. Pipe 11 frosting rosettes around the top edge of the cake with a large French piping tip; pipe one rosette in the middle of the cake. Top each rosette on the outer edge of the cake with a peanut butter cup half. Place four peanut butter cup halves, fanned, on the middle rosette. Sprinkle top of cake with chocolate shavings.
If using the gold sugar, place the cake (on the cake stand or serving platter) in a clean kitchen sink and toss sprinkles onto the sides of the cake. Sprinkle a little on top of the cake, too. Keep cake covered tightly in plastic wrap to prevent loss of moisture.
