These thick, fudgy Marshmallow Swirl Brownies are loaded with gooey marshmallows, crumbled brownie pieces, and chocolate chips on top. I first made these on a rainy Saturday when Liam asked if we could "make brownies but better," and honestly, he was onto something. The best part? No mixer needed, and you get that bakery-style chocolate marshmallow experience right at home.
If you're craving something sweet and gooey, you'll also love my Cherry Chip Cake and Biscoff Cupcakes for more easy dessert ideas.
What Makes These Marshmallow Swirl Brownies Special
There's a reason these Marshmallow Swirl Brownies disappear fast. The base is rich and fudgy, the kind that stays soft in the center with those crispy edges everyone fights over. Then comes the marshmallow layer, all melty and golden, followed by chunks of extra brownie crumbled on top. It's like three desserts in one pan.
The genius part is baking two pans at once. One becomes your base, the other gets crumbled over the marshmallows for texture. It sounds fancy, but it's actually simpler than most Marshmallow Swirl Brownies recipe.
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Marshmallow Swirl Brownies Ingredients
These simple ingredients come together to create rich, gooey Marshmallow Swirl Brownies.
See Recipe Card Below This Post For Ingredient Quantities
- Butter: Melted butter adds richness and helps create that fudgy texture. Regular or dairy-free both work beautifully.
- Granulated sugar: Sweetens the brownies and helps form the shiny top crust.
- Light brown sugar: Adds moisture and a hint of caramel flavor that deepens the chocolate.
- Vanilla extract: Enhances all the chocolate notes and adds warmth.
- Eggs: Bind everything together and give the brownies structure without making them cakey.
- All-purpose flour: Provides just enough structure to hold the brownies together while keeping them soft.
- Unsweetened Dutch processed cocoa powder: Creates that deep, fudgy chocolate flavor. Dutch processed cocoa is less acidic and gives a smoother taste.
- Salt: Balances the sweetness and makes the chocolate flavor pop.
- Mini chocolate chips: Scattered on top for extra bursts of chocolate in every bite.
- Mini marshmallows: Melt into a gooey, golden layer that makes these brownies special. Mini marshmallows melt more evenly than large ones.
How to Make Marshmallow Swirl Brownies
Here's how to make these easy, gooey Marshmallow Swirl Brownies from start to finish.
Prepare the pans: Line an 8×8 inch square baking pan with parchment paper, leaving some overhang so you can lift the brownies out later. Line a 9×5 or 8×4 loaf pan with parchment paper too. Preheat your oven to 350°F.
Make the brownie batter: Melt the butter in a microwave-safe bowl or on the stove. Whisk in the granulated and light brown sugar until the mixture pulls away from the sides and forms a thick paste, about 1 minute. Stir in the eggs and vanilla extract until smooth. Add the flour, cocoa powder, and salt, mixing just until combined. Don't over-mix or the brownies can turn out tough.
Bake the brownies: Divide the batter between your two pans, adding about ⅔ to the square pan and the remaining ⅓ to the loaf pan. Bake both at the same time for 27 to 36 minutes. Start checking around 27 minutes with a toothpick. You want a few wet crumbs clinging to it, not raw batter but definitely not clean.
Prepare the marshmallow layer: Take both pans out of the oven but leave the oven on. Sprinkle the mini marshmallows evenly over the brownie in the square pan. Pop it back in the oven for 4 to 8 minutes, until the marshmallows puff up, turn gooey, and get lightly golden on top.
Add brownie crumbles: While the marshmallows bake, break the loaf pan brownies into chunks with your hands or a fork. Some big pieces, some small. When the marshmallows are ready, scatter the brownie chunks over them, pressing gently so they stick. Finish by sprinkling the mini chocolate chips evenly across the top.
Cool and slice: Let the brownies cool completely in the pan before slicing. This gives everything time to set so you get clean cuts.
Equipment For Marshmallow Swirl Brownies
- 8×8 inch square baking pan: Holds the main brownie layer with marshmallows and toppings.
- 9×5 or 8×4 loaf pan: Bakes the brownies you'll crumble on top.
- Whisk: For mixing the batter smoothly without a mixer.
- Parchment paper: Makes lifting the brownies out easy and cleanup a breeze.
Substitutions and Variations
Dairy-free option: Use dairy-free butter and dairy-free chocolate chips. The recipe works just as well.
Marshmallow fluff: Melt about 2 cups of marshmallow fluff in the microwave and spread it over the Marshmallow Swirl Brownies layer instead of mini marshmallows. It won't puff up the same way, but it's still delicious.
Large marshmallows: You can use them, but they don't melt as evenly. Cut them in half for better coverage.
Extra toppings: Try adding crushed graham crackers, peanut butter chips, or a drizzle of caramel on top.
Gluten-free: Swap in a 1-to-1 gluten-free flour blend. The texture might be slightly different but still good.
Storage Tips
Room temperature: Store the Marshmallow Swirl Brownies unsliced in the pan, covered with foil, for up to 5 days. If you've already sliced them, keep them in an airtight container.
Refrigerator: Brownies will last about a week in the fridge. They'll firm up a bit when cold, which some people actually prefer.
Freezer: Wrap individual brownies in plastic wrap, then place them in a freezer bag. They'll keep for up to 3 months. Thaw at room temperature or warm in the microwave for a few seconds.
Serving Suggestions
With vanilla ice cream: The cold, creamy scoop against the warm, gooey brownie is perfect.
Alongside coffee or hot chocolate: These Marshmallow Swirl Brownies pair beautifully with something warm to sip.
At parties or potlucks: Cut them into smaller squares for bite-sized treats that everyone can grab easily.
As a s'mores-style dessert: Serve them warm with extra graham crackers on the side for dipping.
Expert Tips
Don't overbake. The toothpick should have wet crumbs, not come out clean. Brownies continue cooking as they cool, so slightly underdone in the oven means perfectly fudgy later.
Use parchment paper. It makes lifting the brownies out so much easier and gives you cleaner edges when you slice.
Let them cool completely. I know it's hard to wait, but warm brownies are messy to cut. Give them at least an hour.
Measure cocoa carefully. Too much and the brownies taste bitter. Use the scoop and level method or a kitchen scale for accuracy.
Press the toppings gently. You want the brownie chunks and chocolate chips to stick to the marshmallow layer, but don't smash them down hard.
Watch the marshmallows. They can go from perfectly golden to burnt quickly. Check them after 4 minutes.
FAQ
Can I put marshmallows in my brownie batter?
You can, but they'll mostly dissolve into the batter as it bakes. For that gooey marshmallow layer, it's better to add them on top after baking, like in this recipe.
What is in a Killer brownie?
A Killer Brownie is a trademarked dessert that layers brownies with caramel, pecans, and chocolate. It's richer and more layered than a standard brownie, kind of like these marshmallow swirl brownies with all their toppings.
Are melted marshmallows the same as marshmallow fluff?
They're similar but not identical. Marshmallow fluff is smoother and more stable, while melted marshmallows can be stickier and slightly grainy. Both work in recipes, just with a small texture difference.
What makes brownies fudgy vs cakey?
Fudgy brownies have more fat (butter or oil) and less flour, plus fewer eggs. Cakey brownies have more flour and eggs, which creates a lighter, airier texture. For fudgy results, don't overbake and keep the flour ratio low.
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Pairing
These are my favorite dishes to serve with Marshmallow Swirl Brownies
Marshmallow Swirl Brownies
Ingredients
Method
- Preheat the oven to 350°F (175°C). Line an 8x8 inch square pan with parchment paper, leaving edges hanging for easy removal. Line a 9x5 loaf pan with parchment paper.
- In a microwave-safe bowl, melt the butter. Stir in the granulated sugar and brown sugar until it forms a paste. Whisk well to combine.
- Add eggs and vanilla extract. Whisk until fully incorporated.
- Sift together the flour, cocoa powder, and salt, then add to the wet mixture. Stir until just combined (do not overmix).
- Divide the brownie batter: add two-thirds to the 8x8 inch pan and one-third to the loaf pan. Bake both pans at the same time for 27-36 minutes. Check for doneness by inserting a toothpick-it should come out with a few wet crumbs.
- Once baked, remove the pans from the oven, keeping the oven on. Set the loaf pan aside. Scatter the mini marshmallows evenly over the brownies in the 8x8 pan. Return to the oven and bake for an additional 4-8 minutes, or until the marshmallows are golden and gooey.
- Meanwhile, break the brownies from the loaf pan into small chunks. These will be sprinkled over the marshmallow layer.
- Once the marshmallows have melted, remove the pan from the oven. Sprinkle crumbled brownie pieces over the marshmallows and gently press them into the gooey surface. Evenly sprinkle with mini chocolate chips.
- Allow the brownies to cool completely before removing them from the pan and slicing.
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