In a large saucepan over low heat, melt 4 cups of marshmallows with 1 tablespoon of butter, stirring continuously for about 5 minutes until creamy and smooth.

Immediately pour in 6 cups of Fruity Pebbles cereal, stirring gently with a silicone spatula for about 1-2 minutes until well-coated.

Line a baking sheet or countertop with parchment paper. Spread the marshmallow-cereal mixture onto the parchment, flattening it into a rectangle, roughly 1/2 inch thick.

Starting at one edge of the parchment, roll the mixture into a log shape, press gently but firmly as you roll.

Use a sharp knife to cut the log into bite-sized pieces, serve immediately or store in an airtight container for up to three days.