Peanut Butter Cup Cake

1 devils food cake mix
3 eggs
1 c. buttermilk
1/2 c. vegetable oil
2 c. peanut butter cups {plus more for garnishing}
8 oz. dark chocolate {I used German sweet chocolate and a little milk chocolate},chopped
1 c. heavy cream
1/2 c. peanut butter

Preheat the oven to 350°. Coat 2 9 inch cake pans with non-stick cooking spray. Line with wax paper and coat paper. {I didn't do this and it came out just fine}
In a large bowl, beat cake mix, eggs, buttermilk and vegetable oil on low for 30 seconds. Increase speed to medium-high for 2 minutes. Scrape down sides after 1 minute. Fold in 2 cups chopped peanut butter cups. Pour batter into pans and bake at 350 for 30 minutes or until a toothpick inserted comes out clean. Remember to use a clean hand towel and press cake while hot to even them out. Cool cakes completely. Place chocolate in a medium bowl. Bring cream almost to a boil and then pour over the chocolate. Whisk until smooth add peanut butter and whisk until smooth.
Trim each cake layer so the tops are flat. Place one layer on your cake plate and pour 1 cup frosting onto the top. Spread evenly with a spatula. Add the second layer and pour the remaining frosting over the top and sides of cake. Smooth out with a spatula. Allow frosting to set for a minute and gently press the peanut butter cups all over the top and sides of the cake. Place in the refrigerater for about an hour to set. Remove and serve.