Spray a large rimmed baking sheet (17x11) with non-stick cooking spray- set aside.
Place Oreos in a plastic bag and crush into pieces.
2 Regular Sized Packages Double Stuffed Oreos
In a large sauce pan over medium-low heat melt butter.
½ cup butter
Add in marshmallows. Stir until fully melted.
16 oz mini marshmallows
Remove from heat and stir in the crushed Oreos.
Press the Oreo mixture into prepared baking dish make sure to spread out the mixture to fill the dish. You want this layer to be well packed and thin.
Cover baking sheet with cling wrap and if you have a second baking sheet place it on top of the Oreo mixture and weigh down with something heavy. Allow to cool completely.
Once the Oreo mixture is set, cut in half. Line a 9x13 dish with cling wrap then place an entire half of the Oreo mixture in the lined dish.
Allow ice cream to soften slightly then spread over the Oreo layer in the dish. Place the second half of the Oreo layer on top, cover with more cling wrap and place back in the freezer until ice cream is solid again.
½ gallon cookies and cream ice cream
Once frozen, remove entire Oreo bar/ice cream block from dish (turning the dish upside down helps to get it out along with the cling wrap) and cut into pieces.