Decadent Chocolate Peanut Butter Cake

1. In a medium-sized bowl whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set it aside.
2. In another microwave safe bowl, melt the chocolate and peanut butter together in 30 second intervals, until it is smooth and shiny. Set it aside.
3. Preheat the oven to 350 F. Grease and flour two 9-inch cake pans, and also line them with a round piece of parchment paper.
4. In the bowl of a stand mixer fitted with the paddle attachment cream together the butter and sugar until light and fluffy. Add in the eggs and yolks one at a time, mixing as you go. Mix in the vanilla.
5. Into the mixing bowl add 1/3 of the dry ingredients, followed by 1/2 of the buttermilk, mixing as you go. Repeat. Then finish with the last 1/3 of the dry ingredients.
6. Switch to a rubber spatula and gently fold in the chocolate peanut butter mixture. Evenly divide the cake batter among the two prepared cake pans and bake them for 30 minutes.
7. In the meantime, make the frosting. Combine the chocolate, peanut butter, brown sugar and buttermilk in a heat proof bowl. Put it over a small pot of simmering water and let it melt completely, stirring to make it smooth. Take it off the heat and let it cool.
8. In the clean bowl of the stand mixer beat the butter until it is fluffy. Add in the salt. Pour in the cooled chocolate peanut butter ganache and thoroughly beat it in. Then gradually add in the powdered sugar until you have a luscious frosting,
9. When the cakes are done, take them out of the oven and let them cool. Turn them out onto a plate or rack to completely cool.
10. Invert cakes to be right-side up again. Put one cake onto a serving platter. Frost the top of the first layer, then sprinkle the top of that layer with chopped dry roasted peanuts. Then carefully transfer the other cake layer on top. Frost the whole cake with an offset spatula.
11. Decorate around the edge of the cake with the mini peanut butter cups. Sprinkle the top with more chopped dry roasted peanuts.