In a microwave-safe bowl, melt the butter and marshmallows together on high for about 2-3 minutes, stirring halfway through until smooth.

Once melted, remove from microwave and stir in the rice crispy cereal until fully coated.

Fold in the crushed Oreo cookies into the rice crispy mixture until evenly distributed.

Press the mixture into a greased 9x9 inch baking dish, ensuring it's packed tightly.

Sprinkle the Oreo cookie crumbs on top of the pressed mixture for added texture and flavor.

Allow to cool for about 10 minutes before cutting into squares and serving.