Simply melt ½ cup peanut butter and 2 tablespoons butter in a covered microwave safe bowl.
Add a bag of tiny marshmallows to the peanut butter mix. Microwave for 30 seconds, mix, then microwave for 30 seconds more.
Fold the melted marshmallows, peanut butter, and butter into a large bowl of Apple Jacks.
Pour the cereal mixture into an 8×8 baking pan coated with non-stick cooking spray or lined with parchment paper.
Gently flatten the mixture evenly around the pan.
Place in the refrigerator for 1 hour/freeze for 30 minutes or until the mixture has hardened enough to cut it into pieces.
Store in an airtight container, layered on parchment paper.