If you’re anything like me, sometimes you just need a treat that’s equal parts cozy and downright indulgent. Marshmallow Brownie lovers, this one’s for you! These chewy, fudgy brownies topped with gooey toasted mini marshmallows and a rich homemade chocolate frosting are basically the edible equivalent of a warm hug after a long day. I made these last weekend when life felt a bit overwhelming and let me tell you — as soon as those marshmallows started puffing and toasting in the oven, my kitchen smelled like pure comfort. And yes, there may have been some sneaky bites straight from the pan (shhh, don’t tell).

Detailed Ingredients with measures

18 ounce box brownie mix, plus ingredients on box
2 cups mini marshmallows (grab a handful more if you’re a real marshmallow fanatic!)

Chocolate frosting:
¼ cup salted butter, softened
1 ½ cups powdered sugar
2 Tablespoons unsweetened cocoa powder
2 Tablespoons milk (add a splash more if needed)
½ teaspoon vanilla extract

Method

Preheat your oven to 350ºF. Grab a 9×9″ pan for those thick, chewy brownies, or if you like them a little slimmer, a 9×13″ will do. Spray with non-stick spray or line with parchment to make cleanup easier (because who really loves scrubbing brownie pans, right?).

Mix up the brownie base according to the package instructions. Pour that luscious batter into your prepared pan and pop it in the oven for about 30 minutes. The trick here is to pull it out when it’s almost set but still a little gooey—not overcooked, or the brownies will lose their fudgy magic.

Now for the fun part: sprinkle 2 cups of mini marshmallows evenly over the top and return it to the oven for just 3 more minutes. Watch closely as those marshmallows puff up and toast to a perfect golden hue. It’s mesmerizing, and if you blink, you might miss it! Let the pan cool completely before moving on.

While you wait, whip up that dreamy chocolate frosting. In a large bowl, beat the softened butter with powdered sugar, cocoa powder, milk, and vanilla extract until smooth and creamy. Don’t hesitate to adjust the frosting—add a bit more milk if it’s too thick or more powdered sugar if it’s runny. I’ve accidentally made frosting puddles before (total kitchen oops) so a little patience here pays off.

Once the brownies are cool, dollop spoonfuls of frosting over the toasted marshmallows and spread gently but generously. Cut into 5 by 4 squares and prepare for the smiles as everyone gets their first sticky, chocolatey bite.

Prep Time

10 minutes

Bake Time

33 minutes

Total Time

43 minutes

Servings

Makes 20 bars

These Chewy Marshmallow Brownies with Chocolate Frosting might just become your new “go-to” for whenever life calls for a little extra sweetness. They’re messy, they’re rich, and yes—completely worth every crumb!

Detailed Directions and Instructions

Preheat and prep

Preheat your oven to 350ºF.

Spray a 9×9″ pan with non-stick spray or line with parchment paper for thick brownies.

To make thinner brownies, use a 9×13″ pan instead.

Prepare and bake brownies

Prepare the brownie mix according to the package directions.

Pour the batter evenly into the prepared pan.

Bake for 30 minutes, or until almost done but not overcooked.

Add marshmallows and finish baking

Remove the pan from the oven and evenly sprinkle 2 cups of mini marshmallows over the top.

Return to the oven and bake an additional 3 minutes until marshmallows puff up and toast slightly.

Remove and allow to cool.

Make the frosting

In a large bowl, combine softened butter, powdered sugar, cocoa powder, milk, and vanilla extract.

Beat with electric beaters until smooth and creamy.

Adjust with extra milk or powdered sugar to reach desired consistency.

Frost and serve

Once the brownies have cooled, place spoonfuls of frosting on top of the marshmallows.

Gently spread frosting evenly over the top.

Cut into 5×4 rows with a plastic knife and serve.

Notes

You can add extra mini marshmallows if you like a thicker marshmallow layer.

Use parchment paper for easy removal and thicker brownies.

For thinner brownies, bake in a larger pan but reduce baking time slightly.

If frosting is too thick, add milk gradually; if too thin, add powdered sugar.

Cook techniques

Preparing the pan for perfect brownies

Alright, first things first: prepping your pan right makes all the difference. I usually go for parchment paper when I want those thick, fudgy edges and an easy-peasy lift out. Spray’s fine too if that’s what you have handy. Just remember, if you want thicker brownies, use a 9×9″ pan. For thinner, more brownie bar vibes, a 9×13″ works better. This little detail always trips me up when I’m rushing—once I tossed my batter in a pan that was way too big and ended up with brownies thinner than a cracker. Lesson learned!

Baking the brownies just right

Timing is everything here, my friend. You don’t want your brownies overcooked—they should be fudgy, not cakey or dry. Baking for exactly 30 minutes gives you that almost-done look where the edges are set but the center still jiggles a little. Since ovens can be sneaky (mine runs hot, always), I eyeball mine around 28 to 32 minutes. If you poke the center with a toothpick it should come out with moist crumbs, not wet batter.

Toasting mini marshmallows on top

This step is where the magic happens! When you sprinkle the mini marshmallows on top after the first bake and pop it back in, you get those gorgeous puffy, slightly toasted clouds of sweetness. Keep a close eye though—3 minutes is usually enough. I’ve definitely let mine go a bit too long one time and ended up with marshmallows turned crispy black. No bueno. They should be soft, melty, and just kissed with golden-brown.

Frosting consistency tricks

Making homemade chocolate frosting feels fancy but is totally doable. Start with softened butter—that’s key to avoid lumps. When mixing powdered sugar, cocoa, milk, and vanilla, don’t rush adding the liquid—sometimes you might want a little less or more milk for the perfect spreadable texture. If it’s too thick, splash in milk gradually; too thin, sprinkle in more powdered sugar. It’s like Goldilocks: not too runny, not too stiff. If your frosting stiffens too fast, just give it a quick stir or a few seconds in the microwave on low.

Cutting brownies neatly

Oh, the struggle of cutting gooey marshmallow brownies without turning them into a melted mess. I find using a plastic knife warmed under hot water cuts through the gooey marshmallows better than a metal one. It glides over the marshmallow top easier, keeping those sweet clouds intact on each square. Patience is key here because the marshmallows tend to stick like crazy when still warm—letting the brownies cool fully before cutting helps a lot.

FAQ

Can I use homemade brownies instead of a box mix?

Totally! Homemade brownies work just as well here. Just make sure they’re baked until almost done but not fully set before adding marshmallows. That way, you get that perfect chewy texture with the toasty marshmallow finish.

What if I don’t have mini marshmallows?

No worries! You can chop up regular marshmallows into smaller pieces or even use marshmallow fluff dolloped on top (though the finishing texture will be a bit different). Mini marshmallows just toast more evenly and quickly.

How do I prevent marshmallows from sticking to the knife?

Warm your knife with hot water before each cut, then wipe it dry. The heat prevents sticky marshmallow mess and gives cleaner slices. It’s a little trick I learned the hard way after trying to slice with a cold knife and ending up with gooey chaos.

Can I make the frosting ahead of time?

You sure can! Just store it in an airtight container in the fridge. Before spreading, bring it back to room temp and whisk or rebeat it a bit until it’s smooth and spreadable again.

Why did my marshmallows burn instead of toast?

Oven temps can vary, so try lowering the heat a tiny bit and keep the marshmallow toasting time short—around 3 minutes on 350ºF. Also, watch them closely because marshmallows can go from golden to burnt very quickly!

Is it okay to use a larger pan than recommended?

Using a bigger pan will give you thinner brownies, so the texture will be a bit different—less fudgy, more chewy or cakey. Just watch your baking times as thinner brownies cook faster!

More recipes suggestions and combination

Peanut Butter Swirl Chewy Marshmallow Brownies

Oh, you guys, adding ribbons of peanut butter right into that fudgy brownie batter before baking? Game changer. I once tried this on a lazy Sunday, and spoiler: it got messy but oh-so-worth-it. Just dollop spoonfuls of peanut butter and give a gentle swirl with a butter knife before baking. When you toast those marshmallows on top? The salty-sweet combo will have you sneaking second pieces when no one’s looking.

Mint Chocolate Marshmallow Brownies

If you have one of those “where’s my mint chocolate fix??” moments, mix a teaspoon of mint extract into your chocolate frosting. Then, sprinkle crushed peppermint candies on top of the toasted marshmallows before frosting. I tried this around a Christmas party once — people legit raved and asked for the recipe twice. Tiny peppermint bits add a nice crunch, but they’re subtle enough to not overpower the marshmallow softness.

Salted Caramel Drizzle & Marshmallow Brownies

Here’s a messy but heavenly trick: after frosting your marshmallow-topped brownies, drizzle gooey salted caramel right over everything. I spilled a bit on my counter. No regrets. Seriously, that mix of caramel saltiness with the ooey-gooey marshmallows and rich chocolate frosting sends your taste buds on a wild joy ride. Use store-bought or make your own, but don’t be stingy on the caramel.

Espresso Infused Marshmallow Brownies

When you need a little extra wake-up call, add a teaspoon of instant espresso powder to your brownie batter. It makes the chocolate more intense and gives a beautiful depth. The toasted marshmallows on top almost taste like a cozy campfire with a caffeine kick. Sometimes I don’t even bother with frosting because the espresso flavor is so good with the toasted marshmallow topping.

Crunchy Nut & Marshmallow Brownies

Chop up some walnuts, pecans, or even almonds and sprinkle them into the brownie batter before baking. Then, when adding the marshmallows on top, toss a handful of nuts on there too before the last few minutes in the oven. The combo of crunchy nuts with soft marshmallows makes every bite exciting. I especially love this one when I’m craving texture contrast; it’s like a little surprise party in your mouth.

Orange Zest Marshmallow Brownies

For a citrus twist, grate a bit of orange zest right into the frosting and fold it in gently. That bright, zesty hit against the rich chocolate and toasted marshmallows is unexpectedly delightful. I added this combo during a family bake-off, and my sister kept stealing extras. The orange makes it feel fancy but stays homey enough for couch cuddles and movie nights.

Raspberry Swirl & Marshmallow Brownies

Pureed raspberries swirled into the brownie batter before baking add a tart contrast that perfectly balances the sweet marshmallow topping. Once cooled, add your chocolate frosting, and you’re in major dessert heaven. One time I forgot the frosting, but the raspberry-swirl + marshmallow combo alone redeemed the whole tray. Next time, I totally doubled the raspberry because, yep, it’s that good.

Dark Chocolate Chips & Marshmallow Brownies

For chocolate lovers who just can’t get enough, toss a big handful of dark chocolate chips into the brownie mix plus a few more sprinkled over the marshmallows before baking. The melting chips mixed with toasted marshmallows create an extra gooey, dreamy texture that’s borderline addictive. I learned this lesson the hard way after one batch mysteriously vanished within a day. No regrets whatsoever.