Here's a recipe I first tried when I was in college. The original recipe called for less servings, but as I was sharing these treats with 350 of my closest friends --also known as the Marching Illini--, I was "forced" to figure out how to make a larger batch. So here it is.
A word of warning: this is a VERY sweet treat, due to the frosted corn flakes. If you want to cut down on the sweetness, use plain corn flakes.
2 C marshmallows (about 1 full package)
¾ C (12 Tbsp, or 1½ sticks) butter or margarine
⅔ C smooth peanut butter
12 C frosted corn flakes
In a very large bowl, measure out corn flakes; set aside. Melt butter in a large saucepan over medium heat. Continue to heat until the butter solids gently start to turn brown.
Add marshmallows and stir until completely melted and smooth. Fold in peanut butter until it, too, has completely blended into the mixture. Remove from heat; pour over corn flakes. Stir until well-coated (may need 2 spatulas or spoons to accomplish this). Press mixture into a lightly greased large jelly roll pan (can also be lined with waxed paper) using a buttered spatula.
Let cool completely. Cut into 1 1/2" x 2" bars.
Makes approximately 64 pieces.