First, put your Oreos (about 20) in a sturdy plastic bag to crush them. I like my meat tenderizer for this, but a rolling pin works too. Crush them until they are roughly the same size as your cereal pieces.
Next, put the marshmallows and butter in a microwaveable bowl. Put them in the microwave on high for 1 minute.
Stir immediately. If the mixture does not combine easily, cook for 30 seconds more, stirring again.
While this mixture is still hot, pour in the rice cereal and Oreos. Stir carefully until everything is combined.
Then press into a lightly greased 8×8 pan.
Allow the treats to cool completely.
Turn them out onto a cutting board and cut into 9 pieces. The treats are ready to eat now, but to really dress them up, melt 1/4 cup of milk or white chocolate chips and drizzle over the treats.