Grease a large bowl and add 2 ⅓ cups Rice Krispies cereal.
In a large saucepan, place 2 tablespoons salted butter, 5 ounces of marshmallows (about 20 regular size or 3 cups mini), and ¼ cup semi-sweet chocolate. For a richer chocolate flavor, stir in 1 tablespoon unsweetened cocoa powder.
Place the pan on low heat and melt, stirring frequently, until the marshmallows and chocolate are almost all melted. Remove from heat and continue to stir until the marshmallow and butter mixture is very smooth. Pour the mixture over the cereal and stir until well blended.
Transfer the mixture to the prepared baking pan and gently press evenly. Chill in the refrigerator about 1 hour. Use the wax paper to pull the layer out of the pan and set aside, either at room temperature or in the refrigerator.
After you remove the bottom layer from the baking pan, grease the pan with cooking spray. (You do not need wax paper for this layer.)
Repeat the above instructions to create the bottom layer.
Once you have your top and bottom layers prepared, you're ready for the ice cream! Scoop slightly-softened ice cream on top of the bottom layer. You will need 5 or 6 scoops to completely cover the layer. Use a spatula to press the ice cream down evenly.
Place the other layer of Rice Krispie treats on top of the ice cream.
TIP: Use a sharp knife or dough scraper to cut the treats, while in the pan, into 16 pieces. This will help later when you're treats are fully frozen.
Freeze overnight or for at least 4 hours.
When ready, remove from the freezer and allow the Rice Krispie treats to soften just a couple minutes and ENOY!