Lightly coat a 9x13-inch baking pan with nonstick spray and set aside. Measure out the cereal and both measures of marshmallows. Set aside.
6 cups crispy rice cereal, 5.5 cups mini marshmallows, 0.5 cups mini marshmallows
In a large pot set over medium-low heat, add the butter and melt. Once melted, add the mini marshmallows and stir to coat with the butter. Stir frequently to melt the marshmallow.
4 tablespoons unsalted butter, 5.5 cups mini marshmallows
Once completely melted and smooth, reduce heat to low and stir in half of the cereal. Stir to coat, then add the remaining cereal, extra marshmallows, and sprinkles. Stir and coat the cereal, leaving no loose bits of cereal.
6 cups crispy rice cereal, 0.5 cups mini marshmallows, 1/4 cup sprinkles
Scoop the marshmallow mixture into the prepared pan. Lightly press down with a greased spatula or piece of waxed paper to reach to the edges of the pan.
Let cool for 1 hour, then cut using spring cookie cutters and serve. Store covered with plastic wrap, or in an airtight container, at room temperature.
Notes
Number of servings will depend on how large your cookie cutters are. If you are cutting into squares, you will get 24.
Nutrition information is an estimate based on online calculators and provided as a courtesy. Any nutritional information should be used as a general guideline only.