This peanut butter cookie cake is soft and chewy with a delicious peanut butter flavor. Filled with peanut butter candies and decorated with chocolate frosting - it's perfect if you love peanut butter.
Line the bottom of a 9-inch springform pan with parchment paper and lightly spray the sides with non-stick cooking spray. Alternatively, lightly spray a 9-inch pie plate with non-stick cooking spray.
In a large bowl, beat together the butter, brown sugar and white sugar until fluffy.
Mix in the peanut butter until smooth.
Then mix in the egg, additional egg yolk and vanilla extract.
With the mixer on a low speed, beat in the flour, baking powder and salt until combined.
Stir in the chocolate chips and Reese's Pieces (or whatever mix-ins you're using).
Spoon the cookie dough into the prepared pan and flatten down into an even layer.
Bake in the preheated oven for about 24-28 minutes, or until the top is golden.
Remove from the oven and cool fully if you're adding frosting on top.
Chocolate Frosting
Beat the butter until smooth.
Mix in 1 cup powdered sugar, starting with the mixer on a low speed.
Mix in the cocoa powder.
Mix in the rest of the powdered sugar about ½ cup at a time, alternating with a tablespoon of cream or milk until the desired sweetness and thickness is reached.
If your cookie cake is in a springform pan, unclamp the outer ring of the pan. Carefully lift the cookie cake off the base of the springform and place on a serving plate or cake stand.
Transfer the frosting to a piping bag (I used a 1M tip). Pipe around the edges of the cake. You may have some frosting leftover if you'd like to frost a message on the cake with a thinner piping tip.
Notes
Pan Sizes: This recipe can be made in a 9-inch springform pan or a 9-inch pie plate. The bake time will be about the same. There is too much batter for an 8-inch springform - the top will get too browned before the cookie is properly baked.
Peanut Butter: Make sure to use commercial peanut butter that does not separate. Homemade or natural peanut butter can separate and end up with inconsistent results due to the oil separating.
Eggs: You'll need 2 eggs in total. You'll use 1 whole egg plus just the egg yolk of the second egg. Do not add 2 whole eggs to the cookie cake.
Mix Ins: Use 1 cup in total of your preferred mix-ins. I used ½ cup chocolate chips and ½ cup Reese's Pieces. Feel free to use entirely chocolate chips, peanut butter chips, M&Ms or a combination.
Storage: Store in an airtight container at room temperature for up to 4 days. The cookie will be the softest on the first day.
Nutrition: Details are an estimate only and based on 1 slice with frosting, assuming the cake is sliced into 10 equal-sized pieces and all the frosting is used.