Monster Cookie Brownies
Monster Cookie Brownies combine a rich, fudgy chocolate brownie base with a thick layer of peanut butter oat cookie dough loaded with M&Ms and chocolate chips. They bake together into one spectacular, crowd-pleasing dessert bar that delivers the best of both worlds in every single bite. Perfect for parties, gifting, or any occasion that calls for something extra special.
Equipment
- 9x13 inch baking pan
- Parchment paper
- Large mixing bowls
- Hand or stand mixer
- Rubber spatula
- Microwave-safe bowl or double boiler
Ingredients
Brownie Base
- 1 cup unsalted butter cut into pieces
- 8 oz semi-sweet chocolate chips or chopped chocolate
- 1.5 cups granulated sugar
- 4 large eggs room temperature
- 2 tsp vanilla extract
- 1 cup all-purpose flour
- 0.5 cup unsweetened cocoa powder
- 0.5 tsp salt
Monster Cookie Layer
- 0.5 cup unsalted butter softened
- 1 cup creamy peanut butter
- 0.5 cup granulated sugar
- 0.5 cup packed brown sugar
- 1 large egg room temperature
- 1 tsp vanilla extract
- 0.75 cup all-purpose flour
- 0.5 tsp baking soda
- 0.25 tsp salt
- 1.5 cups old-fashioned rolled oats
- 1 cup M&Ms plus extra for topping
- 0.5 cup semi-sweet chocolate chips
Instructions
- Preheat your oven to 350 degrees F (175 degrees C). Line a 9x13 inch baking pan with parchment paper, leaving a 1-inch overhang on the long sides. Lightly grease the parchment with nonstick spray or butter.
- Make the brownie base: In a large microwave-safe bowl, melt the butter and semi-sweet chocolate together in 30-second intervals, stirring between each, until smooth and fully combined. Let cool for 5 minutes.
- Whisk the granulated sugar into the melted chocolate mixture until combined. Add the eggs one at a time, whisking well after each addition. Stir in the vanilla extract until the mixture is glossy and smooth.
- Fold in the flour, cocoa powder, and salt with a rubber spatula just until no dry streaks remain. Do not overmix. Spread the brownie batter evenly into the prepared pan and set aside.
- Make the monster cookie layer: In a large bowl using a hand or stand mixer, beat the softened butter, peanut butter, granulated sugar, and brown sugar together on medium speed until light and fluffy, about 2 minutes.
- Add the egg and vanilla extract to the peanut butter mixture and beat until fully incorporated, about 1 minute. Scrape down the sides of the bowl as needed.
- Stir in the flour, baking soda, salt, and rolled oats by hand until a soft, cohesive dough forms. Fold in the M&Ms and chocolate chips until evenly distributed throughout the dough.
- Drop heaping spoonfuls of the monster cookie dough all over the brownie batter. Using your hands or a lightly greased spatula, gently press the dough into an even layer covering the brownie base. Press additional M&Ms onto the surface for a colorful finish.
- Bake in the preheated oven for 32 to 38 minutes, until the edges are set and golden and the center has just a slight jiggle. A toothpick inserted in the center should come out with moist crumbs attached, not wet batter. Do not overbake.
- Allow the bars to cool completely in the pan at room temperature for at least 1 hour. For cleanest slicing, transfer the pan to the refrigerator for an additional 30 minutes before lifting the bars out using the parchment overhang and cutting into squares with a sharp knife.
Notes
For the fudgiest texture, pull the bars from the oven when the center still looks slightly underdone. They set as they cool. Always use room temperature eggs and softened butter to ensure smooth batters. Chill before slicing for clean, bakery-style edges. Store leftovers in an airtight container at room temperature for up to 4 days or in the refrigerator for up to 7 days. Freeze individually wrapped bars for up to 2 months.