In a large saucepan over low heat, melt the 3 tablespoons of real sweet cream unsalted butter. Be sure to stir continuously to prevent any browning.
Once the butter is melted, add the entire 10 oz. package of marshmallows. Stir until completely melted and smooth, creating a gooey marshmallow mixture.
In a separate mixing bowl, combine the 6 cups of Rice Krispy cereal and the 18 crushed Nutter Butter cookies. Make sure the cookies are crushed into small pieces to distribute the flavor evenly.
Pour the melted marshmallow mixture into the bowl with the cereal and cookies. Stir gently but thoroughly until everything is combined and all the cereal and cookie pieces are coated.
Carefully fold in the broken chunks of the 2 large movie-size Hershey bars, allowing some pieces to remain chunky for added texture.
Grease your 9x13-inch baking pan lightly with butter or non-stick spray. Pour the mixture into the pan and press it down firmly with the spatula to ensure it holds together.
Allow the treats to cool at room temperature until set, about 30 minutes. Once cooled, use a sharp knife to slice them into squares or rectangles.
