Step 1

Spray an 8x8-inch baking dish with nonstick cooking spray or line with parchment paper. Set aside.

Step 2

In a large microwave-safe bowl, combine marshmallows and butter.

Step 3

Melt the marshmallows and butter in the microwave in 30-second intervals, stirring in between, until melted (about 2 minutes).

Step 4

Add chopped Oreos (reserving ¼ cup for the topping) to the marshmallow mixture and stir.

Step 5

Pour mixture into the prepared 8x8-inch pan and press into the pan with a spatula. Top with reserved chopped Oreo cookies.

Step 6

Place pan in the refrigerator to set for at least 2 hours, up to overnight.