Reese's Peanut Butter Cups Cake

Ingredients for cake:
1 box (18.25 ounces) devil's food cake mix
3 eggs
1 cup buttermilk
1/2 cup vegetable oil
good pinch of salt
2 cups mini Reese's peanut butter cups, chopped, plus 1 1/2 cups more for garnish (about 2 12-ounce bags)

Ingredients for ganache:
12 ounces dark chocolate, chopped
1 cup heavy cream
3/4 cup creamy peanut butter
4 T powdered sugar

Heat oven to 350 degrees F. Coat two 9-inch round cake pans with nonstick cooking spray. Line with waxed paper; coat paper.

In a large bowl, beat cake mix, eggs, buttermilk, vegetable oil and salt on low for 30 seconds. Increase speed to medium-high; beat for 2 minutes, scraping down side of the bowl after 1 minute. Fold in 2 cups of the chopped peanut butter cups.

Divide batter between prepared pans. Bake at 350 degrees F for about 34 minutes, or until a toothpick inserted in the center comes out clean. Let layers cool on a wire rack for 15 minutes. Turn out cakes onto wire racks and cool completely.

Preparing the peanut butter ganache:
Place chopped dark chocolate in a medium-size bowl. Bring cream just to a boil and pour over chocolate. Whisk until chocolate melts. Add peanut butter and powdered sugar, whisking until smooth.

Frosting the cake:
First trim the tops of cakes with a serrated knife.

Put one cake layer on cooling rack and place on a baking sheet. Spread some ganache on top; spread evenly with a spatula. Place remaining cake layer and pour remaining frosting over the top, allowing it to spill over the sides. Smooth top and sides with spatula.

Refrigerate 1 hour to set. Transfer cake to serving plate and garnish with the chopped Reese's peanut butter cups.

Note: Save some ganache as glue, to put on the cake just before adding the chopped Reese's peanut butter cups, then chill to let it set [Frost the cake, then chill, then add a thin layer of ganache again, add the garnish, then chill again.]