Fudgy Marshmallow Brownies with Fluffy Frosting & Magically Delicious Toppings

St. Paddy’s Day is almost here, which means it’s the perfect time to make these Lucky Charms Marshmallow Brownies! They start with a fudgy brownie base—use your favorite homemade recipe or a box mix (I loveGhirardelli). Swirling marshmallow fluff into the batter before baking gives them a gooey touch, and a fluffy green marshmallow frosting makes them even better. Top them with gold flecks and plenty of Lucky Charms marshmallows because you can never have too many colorful marshmallows.

Recipe Rundown

Leprechaun Traps and Lucky Charms Treats

It’s that time again—time to set the perfect leprechaun trap. We’ve done this every year, and I’m fully invested. I wake up expecting to actually catch one, and honestly, I’m a little disappointed every time I don’t. But that just means I have to try again next year.

St. Patrick’s Day is the perfect excuse to add a little mischievous fun into the mix. And lately, I’ve been on a bit of a Lucky Charms kick—partly because I love the cereal, and partly because it’s the perfect match for this holiday.

Brownie Tips for the Best Texture

When making these brownies, go for a fudgy brownie mix or recipe. The cake-like ones just don’t do justice to the swirls of marshmallow fluff baked in. A rich, chewy texture makes all the difference.

Frosting and Toppings

I went with a marshmallow buttercream, but if you want to switch it up, you can use a classic vanilla buttercream with rainbow nonpareils or even add a little something extra with Baileys.

For toppings, I found one of those huge bags of Lucky Charms marshmallows at Target, but if you don’t have them, you can use rainbow sprinkles or even the whole cereal, including the oat pieces. Just make sure to eat the brownies right away or add the toppings just before serving. That way, the marshmallows and cereal stay crisp and don’t get soggy

FAQ

1. Can I use homemade brownie batter instead of a box mix?
Yes! You can substitute a homemade brownie recipe, just be sure to use one that yields a fudgy texture for the best results.

2. How do I store these brownies?
Store them in an airtight container at room temperature for up to 2 days or in the fridge for up to a week. For longer storage, freeze them for up to 3 months.

3. Can I make the frosting ahead of time?
Yes! You can make the frosting up to 2 days in advance and store it in the fridge. Let it come to room temperature and re-whip before spreading.

4. Can I use unsalted butter for the frosting?
Yes, if using unsalted butter, add a pinch of salt to balance the sweetness.

5. How do I get a vibrant green color for the frosting?
Gel food coloring works best for achieving a bold, vibrant green without affecting the consistency.

Sprinkle of Fun

Lucky Charms Marshmallow Decorating Challenge

Take these brownies to the next level with a marshmallow decorating challenge! Set out a bowl of Lucky Charms marshmallows, edible gold flakes, and any other fun toppings like rainbow sprinkles or crushed cereal, like Fruity Pebbles.

Give everyone a frosted brownie and let them create their own masterpiece—maybe a rainbow, a pot of gold, or even their initials spelled out in marshmallows. Snap a picture of the creations before digging in, or let someone be the judge and award a fun St. Paddy’s Day prize.

Lucky Charms Marshmallow Brownies

Print Recipe

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

No reviews

• Author: Taryn Camp

Ingredients

Scale 1x2x3x

For the brownies-

• 1 box of brownie mix plus the ingredients listed on the package
• 1/3 c marshmallow fluff

For the frosting

• 1 cup (2 sticks) salted butter, softened
• 1 ½ cups marshmallow fluff (about one 7 oz jar)
• 2 cups powdered sugar
• 1 tsp vanilla extract
• 1–2 tbsp heavy cream, as needed
• Green food coloring

For the decorations

• Lucky Charms marshmallows
• Edible gold flakes

Cook Mode Prevent your screen from going dark

Instructions

1. Preheat the oven to 350 degrees and line a 9” square baking dish with parchment paper and spray it with baking spray.
2. Prepare the brownie mix according to the package instructions. Pour the batter into the prepared pan, smoothing it into an even layer  drop dollops of the fluff onto the brownie batter and gently swirl it in with a knife. It doesn’t have to be perfect because it’ll bake in to the brownies.
3. Bake the brownies according to the package and then let them cool completely. I love to transfer them to the fridge for an hour or two because it makes them extra fudgy!
4. Meanwhile, in a large mixing bowl, beat the softened butter with an electric mixer on medium speed for about 2 minutes, until smooth and fluffy.
5. Mix in the marshmallow fluff and continue beating until well incorporated.
6. Add powdered sugar, one cup at a time, mixing on low speed at first, then increasing to medium-high. Scrape down the sides of the bowl as needed.
7. Mix in the vanilla extract and a food coloring until you don’t see any streaks of color. If the frosting is too thick, add 1-2 tbsp of heavy cream or milk, a little at a time, until it reaches your desired consistency.
8. Beat on high speed for another minute or two until light, fluffy, and smooth.
9. Spread the frosting onto the cooled brownies. If you don’t want to use it all, set the remaining amount aside for another use. Top with gold flakes and Lucky Charms marshmallows and cut into squares. Enjoy!

Check out my ebook library here! 

Subscribe to my email for secret recipes here!