Preparation Steps

• Preheat oven to 350°F (180°C). Line a 9-inch cake pan with parchment paper and grease the sides. Set aside.
• In a medium bowl, whisk together flour, baking soda, and salt. Set aside.
• In a large mixing bowl, cream the butter, peanut butter, granulated sugar, and brown sugar on medium speed until light and fluffy, about 2-3 minutes.
• Add the egg and vanilla extract to the creamed mixture and beat until well combined.
• Gradually add the dry ingredients to the wet ingredients and mix until just combined. Avoid over-mixing.
• Fold in the chopped peanut butter cups and chocolate chips until evenly distributed.
• Press the cookie dough evenly into the prepared cake pan. Optionally, press a few extra chocolate chips or chopped Reese’s on top.
• Bake for 18-22 minutes, until the edges are golden and the center is just set. Remove from oven and cool completely in the pan.
• Once cooled, remove the cookie cake from the pan and transfer to a serving plate.
• To make the buttercream, beat the butter in a large bowl until smooth. Add 1 cup powdered sugar and mix until combined.
• Add cocoa powder and vanilla extract, then mix thoroughly. Add 1 tablespoon heavy cream and beat until smooth.
• Add remaining powdered sugar and mix until fluffy. Add more heavy cream if needed for desired consistency.
• Pipe the buttercream around the edges of the cookie cake and garnish with halved Reese’s peanut butter cups.
• Store in an airtight container at room temperature for up to 2 days, then refrigerate. Best eaten within 4-5 days. Serve at room temperature.