Start by lining your 9x13 inch baking dish with parchment paper. Leave some overhang on the sides to make it easy to lift the bars out later.
In a medium saucepan over low heat, melt the stick of salted butter. Once melted, add in the 26 ounces of mini marshmallows. Stir continuously until the marshmallows are completely melted and the mixture is smooth. This should take about 5-7 minutes.
Once the marshmallows are melted, remove the saucepan from the heat and stir in 1 teaspoon of vanilla extract.
In a large mixing bowl, add the 10 cups of Golden Grahams cereal. Pour the melted marshmallow mixture over the cereal and gently fold everything together until the cereal is evenly coated.
Carefully fold in the 2 cups of mini peanut butter cups, ensuring they are distributed throughout the mixture.
Transfer the mixture into the prepared baking dish. Use the spatula to press it down firmly and evenly.
Allow the mixture to cool at room temperature for about 1 hour.
