Prepare Your Pan: Lightly butter an 8x8-inch baking dish. Line it with parchment paper, making sure the paper extends up all sides and overhangs at least two edges. This makes lifting the treats out super easy!
Melt the Gooey Base: In a large, microwave-safe bowl, combine your sugar-free marshmallows and salted butter. Microwave in short bursts: start with 30 seconds, give it a good stir, then microwave for another 45-60 seconds until the mixture is mostly melted. Continue stirring until it's completely smooth and wonderfully gooey.
Add Flavor: Quickly stir in the vanilla extract into the melted marshmallow mixture. This adds that classic, comforting taste.
Mix in the Crunch: Working swiftly before the mixture cools and sets, add about half of your chopped protein cereal to the bowl. Stir to coat, then add the remaining cereal, one cup at a time, ensuring everything is evenly covered. Speed is key here, as the mixture sets fast!
Shape Your Treats: Transfer the entire mixture into your prepared baking dish. Gently press it down evenly. To avoid sticking, you can place a piece of parchment paper on top and press, or lightly wet your hands. Remember not to pack it too tightly, or your treats will be dense instead of chewy.
Cool and Set: Let the crispy treats cool completely in the pan at room temperature for about 30-60 minutes until they are firm. (Skip the fridge – chilling them can make them too hard!)
Slice and Serve: Once firm, use the parchment paper overhang to lift the entire block of treats out of the pan and onto a cutting board. Slice into 16 perfect squares. Enjoy your healthy and festive New Year's treat!