In a large saucepan, place 4 tablespoons of butter and heat over medium-low heat. Stir continuously for about 2-3 minutes until melted.

Gradually add 10 ounces of mini marshmallows to the melted butter, stirring often for about 4-5 minutes until nearly melted.

Mix in ½ cup of peanut butter and stir vigorously for 1-2 minutes until smooth and creamy.

Remove the saucepan from heat and fold in one 13-ounce box of Reese’s Puffs cereal until well-coated.

Prepare a greased 9 x 13-inch pan and transfer the cereal mixture into the pan, spreading it evenly.

Gently press the mixture evenly into the pan with wet hands or a greased spoon.

Let the bars sit at room temperature for 30 minutes to set.