Betty Crocker has a good recipe for peanut butter bars. It makes 36 servings and takes a total of two hours and 20 minutes from start to finish.
To make Betty Crocker's peanut butter bars, stir together 1 pouch of Betty Crocker's peanut butter cookie mix, 2 tablespoons of vegetable oil, 1 egg and 1 tablespoon of water, and stir until the mixture forms a soft dough. Coat the bottom of a 13-by-9-inch baking pan with cooking spray, lightly flour your fingers, and press the dough into the pan. Bake in a preheated 350 degree Fahrenheit oven for 15 to 18 minutes or until golden brown before removing the pan from the oven and allowing it to cool for one hour.
To create the filling, blend 1/2 of a cup of soft butter, 1/2 cup of creamy peanut butter, 2 cups of powdered sugar, and 1 teaspoon of milk together using the medium speed setting of an electric mixture, and spread the mixture over the baked and cooled cookie base.
Microwave 1/4 cup of butter and 1 cup of semisweet chocolate chips together for about one minute on high to create frosting, and stir the mixture until it is smooth. After allowing it to cool for 10 minutes, spread it over the filling, and place it in the refrigerator for 30 minutes or until it is set. Cut into 9-by-4 rows, and serve.