Prepare a 9×13-inch pan by spraying it with butter cooking spray. Set aside.
Place the Oreos in a sandwich bag and crush them using a rolling pin or mallet.
In a large pot over medium heat, melt the butter and add salt. Use a rubber spatula to spread the butter up the sides to prevent the mixture from sticking.
Add the sweetened condensed milk to the melted butter and stir until well combined.
Add the 12 ounces of mini marshmallows. Stir over medium heat until the mixture is completely melted. Then remove from the heat.
Add the vanilla extract and stir until well combined.
Quickly mix in the Oreos.
Add the 7 cups of Rice Krispies cereal and use a rubber spatula to stir it all together.
Pour the mixture into the prepared 9×13-inch pan. Wet your hands, shake off the excess water, and use your hands to gently press the Rice Krispies into the pan. Don't press them down too hard, or they'll be hard to bite into.
Add some extra Oreos on top. Let the treats cool at room temperature for an hour.
Using the rubber spatula, remove the treats from the pan. Use a knife to cut them into squares. Enjoy!