To prepare a brownie cookie whoopie pies recipe, first you need to prepare the brownie cookies. First, you'll need the following ingredients: 1 1/2 cups semisweet chocolate chips 1 cup chopped peanuts 1 teaspoon vanilla 2 tablespoons powdered sugar 2 teaspoons butter or margarine Instructions: Preheat the oven to 350 degrees F. Line two 9x9-inch baking pans with foil and set aside. In the bowl of an electric mixer, cream the butter and sugar on medium speed until light and fluffy. Add the eggs and vanilla and beat until combined. Gradually add the flour and mix until the mixture resembles coarse crumbs. Pour the wet mixture into the dry mixture and stir until just combined, about 2 minutes. Then stir in the vanilla. Beat the batter until it's thick and spreadable. Spread the cooled brownie batter evenly over the top of the foil-lined pan. Bake for 18 to 20 minutes or until puffed and golden. Allow to cool before removing from the pan and serving.