Reese's Peanut Butter Cup Cake

When we were visiting Arkansas and my family in April, I decided that since I hadn't had a real "birthday" cake the previous week, I should make something huge and ridiculously outrageous that I would never make for just our family because Grant and I would gain 10 lbs. each in the process.  This cake had caught my eye months earlier and I knew that everyone in my family loves peanut butter and chocolate, so this seemed to be the ideal choice.
It was met with quite positive reviews, I have to say.  The cake itself wasn't my favorite - maybe it was because I used powdered buttermilk with water instead of the real thing, or maybe I over baked it a tad - at any rate, I think next time I'll substitute coffee for the buttermilk.
The frosting - ohhhhhhhhhhh, the frosting.  It is heaven in a bowl.  My sister Anna made it - she made a double batch, which ended up being too much for the cake, but the leftovers were readily eaten with graham crackers as snacks over the next few days.  So so so good.

Recipe: (cake from Annie's Eats, frosting from Ina Garten)

2 cups all-purpose flour
1/2 cup unsweetened cocoa powder
1/2 t. baking powder
1/2 t. baking soda
1/2 t. salt
2 sticks unsalted butter, room temperature
1-1/2 cups sugar
2 large eggs
2 large egg yolks
1 t. vanilla extract
1 c. buttermilk (or 1 cup brewed coffee)
4 oz bittersweet or semi-sweet chocolate, melted and cooled

Frosting: (This is the regular batch - we doubled it and had a lot leftover, which wasn't a bad thing!)
1 cup powdered sugar
1 cup creamy peanut butter
5 T. unsalted butter, room temperature
3/4 t. vanilla extract
1/4 t. salt
1/3 cup heavy cream
1 bag Miniature Reese's cups, halved and or chopped

For the cake, center a rack in the oven and preheat the oven to 350°.  Butter two 9" round cake pans, dust the insides with flour, tap out the excess and line the bottoms with rounds of parchment paper.  Place the pans on a baking sheet.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt  Set aside.

In a large mixer with the paddle attachment, beat the butter on medium speed until soft and creamy. Add the sugar and beat for about 2 minutes, until thoroughly blended into the butter.  Add the eggs and yolks one at a time, beating for one minute after each addition and scraping down the sides of the bowl as needed.  Beat in the vanilla.  Reduce the mixer speed to low and add teh dry ingredients alternately with the buttermilk (or coffee); add the dry ingredients in 3 additions and the buttermilk in 2 (beginning and ending with the dry ingredients).  Mix each addition only  until it is blended into the batter.  Scrape down the bowl and add the melted chocolate, folding it in with a spatula. Divide the batter between the prepared cake pans.

Bake for 26-30 minutes or until the cakes feel springy to the touch and start to pull way from the sides of the pans.  Transfer to wire racks to cool for about 5 minutes, then run a knife around the sides of the cakes, unmold them and peel off the paper liners.  Invert and cool to room temperature right side up.

To make the frosting, place the powdered sugar, peanut butter, butter, vanilla, and salt in the bowl of an electric mixer fitted with a paddle attachment.  Mix on medium-low speed until creamy, scraping down the bowl with a rubber spatula as you work. Add the cream and beat on high speed until the mixture is light and smooth.

To assemble the cake, place one cake layer on the cake stand.  Spread peanut butter frosting on top of the cake layer.  (If desired, sprinkle with chopped Reese's cups).  Place the second cake layer on top of the frosting.  Frost the top and outside of the cake with remaining frosting.  Decorate with halved and chopped Reese's cups as desired.