Grease an 8x8 inch baking pan or line it with parchment paper. Set aside.
In a large saucepan, melt the butter over low heat. Add the entire bag of mini marshmallows and stir until completely melted and well combined with the butter. Stir in the vanilla extract.
¼ cup unsalted butter, 10 oz mini marshmallows, 1 teaspoon vanilla extract
Pour the cinnamon toast crunch cereal mixture into the melted marshmallows. Stir quickly to coat the cereal evenly with the marshmallow mixture. Once coats, add in the extra mini marshmallows if you'd like and mix to combine again.
6 cups Cinnamon Toast Crunch cereal, 5 oz mini marshmallows
Transfer the mixture to the prepared baking pan. Use a spatula or your hands (lightly greased) to press it firmly and evenly into the pan. If desired, sprinkle additional crushed up Cinnamon Toast Crunch cereal on top and gently press it into the mixture for added crunch and flavor.
Cinnamon Toast Crunch cereal for topping
Allow the rice krispie treats to cool and set at room temperature for at least 1-2 hours, or you can refrigerate them for a quicker setting. Once the treats are completely set, cut them into squares or rectangles of your desired size.