Step 1

Preheat oven to 350°F (177°C). Spray a 9×2 inch cake pan (or 9-inch springform pan) with nonstick spray. Set aside.

Step 2

Using a handheld or stand mixer, beat the butter and brown sugar together on medium speed in a large bowl until creamed. About 2-3 minutes. Add eggs, one at a time, and beat until combined. Scrape down the sides of the bowl as needed. Add the peanut butter and vanilla extract, beating for about 2 full minutes. Set aside.

Step 3

In a medium sized bowl, toss together the flour, baking powder, and salt. Slowly add the dry ingredients to the wet ingredients in 3 additions, stirring by hand after each addition. Batter will be thick. Add the buttermilk and mix until just combined, do not overmix.

Step 4

Spoon the batter into the prepared cake pan. Bake for 20 minutes. Remove from the oven and loosely cover with aluminum foil. Bake for an additional 12-13 minutes or until a toothpick inserted in the center comes out clean. Allow cake to cool completely in the pan on a wire rack.

Step 5

* In a medium sized bowl, beat the cream cheese on medium-high speed until smooth and creamy. Turn off the mixer, add the marshmallow creme and beat on low speed for 1 minute. Slowly add the powdered sugar and vanilla extract and beat for 1 minute. Add the salt and continue to beat. Add more powdered sugar if you’d like the frosting to be thicker. Add more salt to cut that extra sweetness.

Step 6

Remove the cake from the pan by inverting it onto a large plate or cake stand. Frost the cake as desired. There will be leftover frosting depending how much frosting you use. Decorate with chopped Reese’s Cups. Cake stays fresh (covered) at room temperature or in the refrigerator for 4 days. Frost immediately before serving.