Step 1

Line an 8x8 pan with foil or parchment paper.

Step 2

Place the white chips and butter in a large pan over low to medium heat. Stir until melted and creamy. It will not be runny, just thick and creamy.

Step 3

Remove the foil lid from the frosting and microwave for 30 seconds. Pour the melted frosting into the pan. Stir the mixture until everything is melted and creamy. Let cool for 10 minutes, stirring occasionally.

Step 4

Stir in 1 1/2 cups marshmallows and half the sprinkles quickly. Pour the fudge into the prepared pan.

Step 5

Sprinkle the top of the fudge with the remaining 1/2 cup marshmallows and sprinkles. Let set completely before cutting into squares.