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!
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!
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.
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!
Four years ago: Homemade Hostess Cupcakes
Five years ago: Peanut Butter Blondies
Six years ago: Cranberry White Chocolate Chip Cookies
Fudge Ripple Monster Cookie Bars
- 1⅓ cups (166.67 g) all-purpose flour
- ⅔ cup (54 g) old-fashioned rolled oats
- ½ teaspoon (0.5 teaspoon) baking soda
- ½ cup (113.5 g) salted butter, at room temperature
- ½ cup (110 g) light brown sugar
- ¼ cup (50 g) granulated sugar
- ¾ cup (193.5 g) creamy peanut butter
- 1 egg
- 1 teaspoon vanilla extract
- ¾ cup (177.44 g) M&Ms
Fudge Ripple Filling
- 7 ounces (198.45 ml) sweetened condensed milk
- 1 tablespoon salted butter
- 1 cup (180 g) semisweet chocolate chips
- 1 teaspoon vanilla extract
- Preheat oven to 350 degrees F. Line the bottom and sides of an 8x8-inch baking pan with aluminum foil, leaving an overhang on all sides. Set aside.
- Make the Bars: In a large bowl, whisk together the flour, oats and baking soda.
- 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.
- 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.
- 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.
- 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.
- 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.
Did you make this recipe?
Leave a review below, then snap a picture and tag @thebrowneyedbaker on Instagram so I can see it!
I made these to take to a small group event and everyone loved them! I doubled the recipe and baked them for 26 minutes and they came out perfect. The only change I made was to use half of the dough on the bottom and half on the top, so there was full coverage on top. Delicious…I will add these to my baking rotation.
I doubled the recipe and baked in a 9×13 pan for about 35 minutes. Probably over baked by a few minutes, but still tasty. Thanks!
Hi Michelle…have you tried doubling this one? I see in the comments below that it can be but just curious if anyone has attempted. If not, I may be the guinea pig! I am thinking cook time will be around the same. Do you agree?
Do these freeze well?
Hi Carolyn! Yes, they do!
I made these bars for a bake sale and they were delicious! I doubled the recipe and added an extra egg to the cookie dough to make them a little softer. I also used pretzel M&Ms in the topping which was a great addition of salt and crunch!
Made these for our super bowl party. They were a big hit! They are similar to some m&m bars my mom has been making for years. This recipe has inspired me to tweak my mom’s recipe to add peanut butter. Thanks for so many great recipes!
the fudge monster bars are the best thing ever sooooo good
Unlike everyone else (it seems), I did not have great results with this recipe. I really wanted to. Your pictures are fantastic. I’ve been testing your recipes for years. Mine turned out a bit dry, too thick, slightly crumbly and not as rich-tasting as I would have preferred. I’m not really a fan of peanut butter cookies ~ and this could be part of my problem. I did not over-mix, so I don’t think that was an issue. Is there a way to make these bars more moist and richer-tasting? BTW ~ I’m thinking of testing another recipe tonight! Can’t wait…
Hi Susan, If you don’t like peanut butter cookies, that could definitely be part of the problem. My only suggestion would be to make sure that you haven’t overbaked them, which could cause them to be dry and crumbly.
I’m curious to know what type of Sunbutter you used – Natural version (yellow) or the Creamy (red) ? I have an allergy and do sometimes bake with the natural Sunbutter, but I wasn’t sure if that was too runny for these bars?
Thank you!!! Love all your recipes – especially the Irish Car Bomb cupcakes for St. Patty’s :)
Could these be doubled for a 13 x 9 pan? Bake time if doubled also?
Yes, can definitely be doubled! I don’t know that the baking time would need to be doubled, though.
Hi Melissa! I used the natural version (yellow lid). Enjoy! :)
Hey, I just noticed, but I like that you are including grams for weight measurements in your recipes! Much more accurate to weigh things and grams is even more accurate than oz! Especially since my scale won’t go to the hundredths place, ie if something calls for 1.75 oz, I have to choose between measuring 1.7 or 1.8 which, I usually round up. Great job and the kids look cute!
Made these for a team meeting today and the guys loved them! Next time I might refrigerate them a bit before slicing – the fudge was still oozy at room temperature (not a bad thing, just messy!) Definitely a keeper. Thanks!
Ah ha! I figured out why the fudge was oozing- I used a whole can of sweetened condensed milk and in re-reading the recipe, it sound like I should have used half a can. Or just doubled the whole recipe and put it in a 9×13. It was still very very good, just a bit messy and sticky. I will definitely make this again!
Made them again – doubled the recipe and used a jelly roll pan (10.5 x 15.5 inches). Worked great. With the correct ratio of sweetened condensed milk to chocolate chips the fudge was the perfect consistency.
What if you wanted to omit the peanut butter, could you do that without other alterations to the monster portion of the recipe.
Hi Lisa, I would increase the butter by the same amount.
These look pretty incredible. These look like you can’t stop at one, so it’s a good thing they only make an 8 x 8 pan. Otherwise, I’m pretty sure I’d make myself sick devouring the entire pan alone! Can’t wait to dip into that fudge filing. But doing a Whole30, so this will have to wait . . . .
I’m so happy you choose these to make. They’re one of my favorite recipes in the book! That fudge layer is absolutely divine.
I have made monster cookies many times. I love them. But even it I didn’t the Fudge Ripple would sell me fast! That is a great idea and makes for a very moist bar I bet. I can see these at a Super Bowl party real soon! Thanks for sharing.
Wishes for tasty dishes,
I first had monster cookies in my youth. We had gone to a big flea market in Ohio and the Amish were selling them.
I’m aurprised Joseph can have M&Ms, with his peanut allergy. I accidentally sent some to my son’s preschool without reading the label. It says that they may contain traces of peanuts. I never knew there was a risk of cross contamination in them.
Yum! I definitely will be making these bars! Thanks for sharing the recipe, Michelle!
I have to try it! These look absolutely delicious! Thanks for the recipe :)