Butter an 8 x 8-inch or 9 x 9-inch baking dish. Set aside.
Work in batches (make a separate batch for each color), and combine butter, marshmallow Peeps, and mini marshmallows in a large saucepan over low heat. Stir constantly until the ingredients are melted and well mixed.
6 ounces Pink Marshmallow Peeps, 1 ½ tablespoons unsalted butter, 1 cup mini marshmallows
Add the rice cereal, and stir to coat. Remove from heat, and transfer the mixture to the prepare baking dish.
3 cups crisped rice cereal
Use buttered hands or a buttered spatula to press the marshmallow treats into an even layer. Allow the treats to cool for about 20 minutes before adding the next color layer.
Repeat the process for the remaining layers making sure to allow each layer to cool before adding the next.
Let the last layer cool completely before cutting and serving. For storage, wrap tightly in plastic wrap and enjoy within 2 to 3 days. Do not refrigerate.
Notes
*The calories listed are an approximation based on the ingredients in the recipe card and a serving size of 1 square. Actual calories will vary.*For more information, tips, and answers to frequently asked questions, please refer to the post.*We used 2 packages of blue marshmallow Peeps, 2 packages of pink marshmallows Peeps, and 2 packages of purple marshmallow Peeps for each layer. Each package contained a total of 8 Peeps for a total of 16 Peeps per layer. Please see the post for more information about using Peeps in Rice Krispie Treats. It does change the texture.