Save This over-the-top brownie slab has become my holiday baking signature. The combination of fudgy chocolate base loaded with colorful M&Ms and gooey marshmallow swirls creates the perfect festive chaos that disappears within minutes at any gathering.
I first created this recipe during a chaotic holiday season when I needed something impressive but didn't have time for complicated baking. My family went absolutely wild for it, and now it's requested at every holiday gathering.
Ingredients
- Unsalted butter: The melted butter creates a rich foundation and fudgy texture. Use high-quality European butter for extra richness
- Granulated sugar: Provides sweetness and helps create that classic crackly brownie top
- Light brown sugar: Adds moisture and a subtle caramel note that complements the chocolate
- Large eggs: Provide structure and richness. Room temperature eggs incorporate better
- Vanilla extract: Use pure vanilla extract for the best flavor profile
- All-purpose flour: Just enough to provide structure without making the brownies cakey
- Unsweetened cocoa powder: Creates deep chocolate flavor. Dutch-processed gives a darker color and smoother taste
- Salt: Enhances all the flavors and balances the sweetness
- M&Ms: The star of the show. Holiday colors make this extra festive. The candy shells add delightful crunch
- Semisweet chocolate chunks: Create pockets of melty chocolate throughout. Chop high-quality chocolate bars for best results
- Mini marshmallows: These create gooey pockets and add visual appeal when swirled
- Chopped walnuts or pecans: Optional but add wonderful texture contrast and nutty flavor
- Festive sprinkles: Optional finishing touch that makes the dessert even more celebratory
Instructions
- Prepare the pan:
- Line your 9x13-inch baking pan with parchment paper, leaving overhang on the sides. This makes removal and slicing much easier later. A light spray of cooking oil helps the parchment stick to the pan corners.
- Mix wet ingredients:
- In a large bowl, whisk the melted butter with both sugars until completely smooth and slightly thickened, about 2 minutes of vigorous whisking. The mixture should look glossy and the sugar should begin to dissolve.
- Add eggs and vanilla:
- Beat in each egg individually, waiting until one is fully incorporated before adding the next. This creates a silky emulsion that helps with the texture. Add the vanilla and mix until just combined.
- Incorporate dry ingredients:
- Sift the flour, cocoa powder, and salt directly into the wet mixture. This prevents cocoa lumps and ensures even distribution. Using a spatula, fold gently with a figure-eight motion until no dry streaks remain, but stop as soon as they disappear. Overmixing will develop gluten and make tough brownies.
- Add mix-ins:
- Gently fold in half of the M&Ms and chocolate chunks, distributing them evenly throughout the batter. The folding motion preserves air in the batter and prevents the candies from bleeding color.
- Transfer to pan:
- Spread the thick batter evenly in your prepared pan, using an offset spatula to smooth the top. Take your time here to ensure even baking and consistent thickness throughout.
- Create the chaos topping:
- Scatter the remaining M&Ms, chocolate chunks, marshmallows, and nuts across the top. Press them lightly into the batter so they stick but remain visible. Use a butter knife to create artistic swirls, dragging through the marshmallows for a marbled effect.
- Bake to perfection:
- Bake in your preheated oven for exactly 28-32 minutes. The center should still look slightly underdone but the edges will be set. A toothpick inserted will come out with moist crumbs but not wet batter. Remember that brownies continue cooking from residual heat after removal.
- Finish with flair:
- Immediately after removing from the oven, sprinkle with festive sprinkles which will slightly melt onto the surface. Let cool completely in the pan for at least 2 hours before lifting out by the parchment paper and cutting with a sharp knife.
Save My absolute favorite part of this recipe is the moment when you pull it from the oven and the marshmallows are perfectly puffed and golden. It reminds me of watching my grandmother make rocky road fudge during the holidays, with that same magical combination of chocolate and marshmallow.
Perfect Slicing Technique
Getting clean cuts through this chaotic masterpiece requires a bit of technique. For perfect squares, refrigerate the completely cooled brownies for 30 minutes before cutting. Run a large sharp knife under hot water, wipe dry, and make clean, decisive cuts. Repeat the hot water rinse between each cut. This prevents the marshmallow from sticking and gives you bakery-worthy presentation.
Make-Ahead and Storage Options
These chaos brownies actually improve with a day of rest as the flavors meld together. Store cut brownies in an airtight container at room temperature for up to 3 days. For longer storage, wrap individual squares in plastic wrap and freeze for up to 3 months. Thaw at room temperature for about an hour before serving.
Seasonal Adaptations
This recipe transforms beautifully throughout the year with simple swaps:
- Valentine's Day Use red and pink M&Ms and add freeze-dried strawberries
- Easter Swap in pastel M&Ms and sprinkle with crushed mini eggs
- Halloween Use orange and black M&Ms and add crushed Oreos for a spooky effect
Serving Suggestions
While these brownies are spectacular on their own, they reach new heights of decadence when served warm with a scoop of vanilla ice cream. The contrast between the warm, fudgy brownie and cold ice cream creates a sensory experience your guests will rave about. For an extra special touch, drizzle with warm caramel or chocolate sauce before serving.
Save The combination of sweet and salty, chewy and crunchy makes these brownies a textural and flavorful delight. They are perfect for any occasion that calls for a little bit of happy chaos.
Recipe FAQ
- → How do I get a fudgy, not cakey, texture?
Don't overmix your batter and bake only until the center is just set. Overbaking leads to a cakier crumb.
- → Can I substitute other candies for M&Ms?
Yes, use your favorite seasonal candies or chocolate pieces for a custom twist on the classic combination.
- → How do I swirl in the marshmallows?
Add marshmallows on top of the batter and use a knife to gently swirl them in for a marbled finish.
- → What is the best way to cut the slab cleanly?
Let the brownie cool completely in the pan, then use a sharp knife cleaned between cuts for neat squares.
- → Can I store leftovers and how long will they last?
Keep in an airtight container for up to 5 days at room temperature or freeze for up to 3 months.