In a large saucepan, melt the butter over low heat. Once melted, add about 8 cups of the marshmallows. Stir constantly until the marshmallows are completely melted and smooth. Keep the heat low so nothing burns.

Remove the pan from heat. Stir in vanilla extract and a small pinch of salt. Then gently fold in the Fruity Pebbles cereal until everything is evenly coated.

Add the remaining 2 cups of marshmallows and stir just until mixed. This creates little pockets of soft marshmallow throughout the treats.

Transfer the mixture to the prepared pan. Gently press it down using a spatula or lightly buttered hands. Don’t press too hard—light pressure keeps the treats soft and chewy.

Let them cool at room temperature for about 30 minutes. Once set, cut into squares and serve.