Melt 4 tablespoons of unsalted butter in a large pot over medium-low heat, stirring continuously for 2-3 minutes until completely melted.

Add 10 ounces of mini marshmallows to the melted butter and stir until fully melted and mixture is smooth, about 2-3 minutes. Remove from heat.

Gently fold in 6 cups of Fruit Loops cereal until coated with the marshmallow mixture, taking care not to crush the cereal, about 1-2 minutes.

Transfer the mixture into a greased 8x8 inch baking pan and press down firmly to create an even layer for about 2 minutes.

Let the mixture cool at room temperature for 30 minutes, then refrigerate for at least 1 hour.

Once chilled, slice into squares with a sharp knife and serve or store in an airtight container.