Fudge Ripple Monster Cookie Bars

Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

Please, pretty please, tell me that you’ve heard of monster cookies or monster bars. If not, let me introduce you to one of my favorite combination of ingredients that you’ll find in any cookie or bar…

The dough typically includes peanut butter, oats, and M&Ms, which makes them one of the most popular little treats you’ll lay your hands on. I’ve made some variations over the years – monster cookies yearssssss ago, then followed those up with monster cookie bars and peanut butter lover’s monster cookies.

When I saw this new version in Sally’s cookbook, with a layer of fudge running through the center, I HAD to make them!

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Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

The beauty of monster bars like these is that, even though they involve the extra step of a fudge center, they are incredibly easy to mix together and you can have them in the oven in no time. Plus, it’s highly likely that you have everything you need to make these sitting in your pantry already. Aren’t those the best kind of recipes?!

Don’t get freaked out by the word fudge! It can be so finicky to make actual fudge, right? Not this filling – it’s incredibly easy. All you need is some sweetened condensed milk, chocolate chips, butter and vanilla, then just heat it until melted, and you’re done. Honestly, I could probably just sit and eat the fudge filling with a spoon.

Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

While I will always and forever prefer peanut butter over alternatives, I did make these successfully with Sunbutter because of Joseph’s peanut allergy. So if you need to make a similar substitution, you shouldn’t have any issues. I didn’t make any other adjustments, and they came out just fine.

If you’ve yet to meet a cookie with peanut butter, oats or chocolate that you didn’t like, then you will go bananas for these fudge ripple monster cookie bars!

Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

Four years ago: Homemade Hostess Cupcakes
Five years ago: Peanut Butter Blondies
Six years ago: Cranberry White Chocolate Chip Cookies

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Fudge Ripple Monster Cookie Bars

Monster cookie bars with the classic combination of peanut butter, oats, and M&Ms, plus a layer of fudge running through the center!

Ingredients:

Monster Bars

  • 1⅓ cups (170 grams) all-purpose flour
  • ⅔ cup (60 grams) old-fashioned rolled oats
  • ½ teaspoon baking soda
  • ½ cup (115 grams) salted butter, at room temperature
  • ½ cup (100 grams) light brown sugar
  • ¼ cup (50 grams) granulated sugar
  • ¾ cup (185 grams) creamy peanut butter
  • 1 egg
  • 1 teaspoon vanilla extract
  • ¾ cup (150 grams) M&Ms

Fudge Ripple Filling

  • 7 ounces sweetened condensed milk
  • 1 tablespoon salted butter
  • 1 cup (180 grams) semisweet chocolate chips
  • 1 teaspoon vanilla extract

Directions:

  1. Preheat oven to 350 degrees F. Line the bottom and sides of an 8×8-inch baking pan with aluminum foil, leaving an overhang on all sides. Set aside.
  2. Make the Bars: In a large bowl, whisk together the flour, oats and baking soda.
  3. Using an electric mixer, beat the butter, brown sugar and granulated sugar on medium speed until light and fluffy, about 2 to 3 minutes. Add the peanut butter, egg, and vanilla one after the other, mixing well after each addition. Scrape down the sides of the bowl as needed. Reduce the mixer speed to low and gradually add the dry ingredients, mixing until just combined. Do not overmix.
  4. Press two-thirds of the dough evenly into the prepared baking pan. Stir the M&Ms into the remaining dough. Set aside while you make the fudge ripple filling.
  5. Make the Fudge Ripple Filling: In a small saucepan over low heat, combine the sweetened condensed milk, butter and chocolate chips. Stir until the chocolate chips are melted and the mixture is smooth. Remove from the heat and stir in the vanilla. Pour the fudge over the bottom layer of dough.
  6. Mold the remaining dough containing the M&Ms into flat pieces and layer on top of the fudge filling. You won’t have enough dough to make one single layer, so some of the filling will be exposed.
  7. Bake for 25 minutes, or until the top is lightly browned. Allow to cool completely. Lift the foil out of the pan using the overhang on the sides and cut into bars. Store in an airtight container at room temperature or in the refrigerator for up to 1 week.

Recipe Notes:

I substituted Sunbutter for the peanut butter in this recipe and it worked just fine.

Did you make this recipe?

Leave a review below, then snap a picture and tag @thebrowneyedbaker on Instagram so I can see it!

(Recipe is excerpted from Sally’s Baking Addiction cookbook by Sally McKenney. Reprinted with permission from Race Point Publishing.)

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