Fudge Ripple Monster Bars


These bars were one of the desserts I prepared for my SIL’s baby shower. I thought the mix of cookie, oats, peanut butter, fudge, and M&Ms was the perfect combination for such an occasion.


I don’t often bake recipes with peanut butter because of my wife’s “allergy”, but baking for a crowd gave me an excuse to try out a peanut butter recipe. I doubled the recipe for an 8″ x 8″ pan and baked it in a 9″ x 13″ pan, which enabled the top layer to mostly cover the fudge ripple because math.


I was really happy with how these bars turned out. The fudge layer is the best part. The cookie is not too shabby either, and the M&M’s provide a nice chocolate crunch to balance the softness of the rest of the bar. My SIL enjoyed these bars so much that she almost didn’t have room for a slice of her cake (the main attraction)! I’ll file that away for future reference…


Based on a recipe in this book.


Monster Bars:
2 2/3 cups (340 g) all-purpose flour
1 1/3 cups (120 g) old-fashioned rolled oats
1 tsp. baking soda
1/2 tsp. salt
1 cup unsalted butter, room temperature
1 cup (200 g) light brown sugar
1/2 cup (100 g) granulated sugar
1 1/2 cups (185 g) creamy peanut butter
2 eggs, room temperature
2 tsp.  vanilla extract
1 1/2 cups (300 g) M&Ms

Fudge Ripple:
14 oz. sweetened condensed milk
2 tbsp. unsalted butter
2 cups (360 g) semi-sweet chocolate chips
2 tsp. vanilla extract
Pinch of salt


  1. Heat oven to 350 degrees. Line the bottom and sides of a 9″ x 13″ baking pan with aluminum foil, leaving an overhang on all sides.
  2. For the bars: In a large bowl, whisk flour, oats, and baking soda.
  3. In the bowl of a stand mixer with paddle attachment, beat butter and sugars on medium speed for 2-3 minutes.
  4. Add the peanut butter, egg, and vanilla, mixing after each addition and scraping the sides of the bowl as needed.
  5. Reduce mixer speed to low, then slowly add the dry ingredients until just combined.
  6. Press 2/3 of the dough into the prepared baking pan.
  7. Stir the M&Ms into the remaining 1/3 of the dough.
  8. For the fudge ripple: In a small saucepan over low heat, melt together sweetened condensed milk, butter, and chocolate chips until the mixture is smooth.
  9. Remove from heat, then stir in the vanilla.
  10. Pour fudge over the bottom layer of dough.
  11. Mold the M&M dough into flat pieces and layer on top of the fudge filling (some fudge will likely show through).
  12. Bake for 25-30 minutes or until top is lightly browned. Allow to cool completely before lifting bars out of the pan.
  13. Cut into bars as desired and serve.