Step 1

Coat an 8-inch square baking dish with cooking spray, then line with waxed paper, extending over sides. Spray waxed paper with cooking spray.

Step 2

In a large pot over medium-low heat, melt marshmallows and butter, stirring frequently. Let cool 5 minutes. Stir in remaining ingredients.

Step 3

Spoon mixture into prepared baking dish and firmly pack down with a spatula (coated with cooking spray to prevent sticking). Cool until firm.

Step 4

Remove from baking dish, peel off waxed paper, and cut into squares.