Peanut butter Rice Krispies treats are similar to regular Rice Krispies treats, except you add peanut butter to the heated marshmallow mixture used to hold the cereal together. A good ratio of ingredients is 6 cups of puffed rice cereal to 1/2 cup of peanut butter to 4 cups of miniature marshmallows.
Start by greasing your 13 by 9 inch baking pan. Melt 6 tablespoons of butter in a saucepan, then add 4 cups of miniature marshmallows and stir until those melt. Remove the pan from the heat and stir in 1/2 cups of peanut butter until you've thoroughly mixed and melted all the ingredients. Next, add six cups of puffed rice. Stir until all the rice is coated, then press the mixture into the baking pan, and wait until it cools before eating.
Alternately, you can heat the ingredients in a microwave. Microwave 3 tablespoons of butter and 4 cups of miniature marshmallows on high for three minutes. Stir, add 1/2 cups peanut butter, and stir again. Next, mix in the puffed rice, and spread into a pan.
You can use chunky or smooth peanut butter, depending on your preference. You can add additional ingredients to further personalize your peanut butter Rice Krispies treats, including whole peanuts and a melted chocolate top layer.