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Marshmallow Buttercream Frosting with Mini Marshmallows

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This fluffy buttercream has real marshmallows mixed right into the frosting. It is relatively stable, super delicious and lots of fun.

Piped swirl of fluffy white marshmallow buttercream frosting.

Picking a frosting to finish of a cake or batch of cupcakes is a big decision. There are so many varieties and flavors to choose from!

Little Dude requested a chocolate and vanilla cake for his birthday. So we ended up making a four layer cake with alternating layers of chocolate and funfetti cakes.

We knew we were going to be making building blocks out of marshmallow fondant. It was the perfect way to decorate a cake for his lego party.

Small cake frosted with marshmallow buttercream and decorated with fondant blocks.

Because of the colorful decorations, we wanted a bright white background. It would have been easy to just make American buttercream or a slight twist on that like sweetened condensed milk buttercream.

But the marshmallow fondant had me in the mood for more marshmallow goodness, so marshmallow fluff buttercream seemed like the perfect base. The only problem was I didn’t have any marshmallow fluff.

I did, however, have some extra marshmallows on hand. The first batch made more blocks than we expected, so we didn’t need to make more like we had anticipated.

So I made buttercream out of marshmallows instead! And you know what? It was delicious!

Getting your frosting ready

If you are going to have a buttercream built on marshmallows, you have to melt those marshmallows. I find the easiest way is to use a large glass bowl in the microwave.

Start with about a minute and then use short bursts until the marshmallows can be stirred smooth. Add a little milk to loosen them up.

Beat some butter until it is smooth and creamy. Now add the melted marshmallows and mix well.

It should make a smooth glossy mixture. Some slight stringing is ok.

If you happen to have some meringue powder, go ahead and add some in. The marshmallows and meringue powder will help to add some stability to your final buttercream.

If you don’t have the meringue powder, don’t despair. The frosting will still work without it.

A little powdered sugar, vanill and more milk is all it takes to finish off the recipe. Adjust with a little more milk or powdered sugar to get you desired consistency.

I personally prefer a softer frosting for spreading and a tighter frosting for piping. It’s easy to adjust to your liking.

Decorating your cake

To make the cake, I piled plenty of frosting between the layers. Even at the looser consistency, it held its own under the weight of the top layers.

The crumb coat went on easily as well. After a quick chill to set the crumb coat, we lathered on the final coat.

It smoothed out nicely and was plenty sticky for Little Dude to arrange his lego blocks wherever he wanted. We also did a little cake just for him!

That way he could blow out his candle without blowing on the whole cake. We jokingly called it his smash cake and he took it seriously.

Boy putting his face into a cake.

He ended up eating it with his face. It was funny even if it was messy!

Piped swirl of fluffy white marshmallow buttercream frosting.

Marshmallow Buttercream Frosting with Mini Marshmallows

Servings: 36 Servings
Author: Carlee
This fluffy buttercream has real marshmallows mixed right into the frosting. It is relatively stable, super delicious and lots of fun.
4.71 from 24 ratings
Prep Time 12 minutes
Cook Time 5 minutes
Total Time 17 minutes


  • 16 oz mini marshmallows
  • 3 Tablespoons milk and more as needed
  • 1 cup unsalted butter soft
  • 1 cup shortening
  • 4 cups powdered sugar
  • teaspoons vanilla extract
  • ¼ teaspoon salt
  • 2 Tablespoons meringue powder optional


  • Melt marshmallows in large microwave safe bowl in 30 second bursts until it can be stirred smooth. Stir in milk, set aside to cool a bit.
    16 oz mini marshmallows, 3 Tablespoons milk
  • Meanwhile beat the butter until it is smooth and creamy. Add the shortening and beat until combined.
    1 cup unsalted butter, 1 cup shortening
  • Add melted marshmallow mixture and mix well.
  • Stir in powdered sugar, salt, meringue powder and vanilla. Mix on low for several minutes.
    4 cups powdered sugar, 1½ teaspoons vanilla extract, ¼ teaspoon salt, 2 Tablespoons meringue powder
  • Adjust the consistency with more milk or powdered sugar as needed.


Serving: 1ServingCalories: 187kcalCarbohydrates: 23gFat: 11gSaturated Fat: 6gPolyunsaturated Fat: 5gCholesterol: 17mgSodium: 67mgSugar: 20g

Nutritional Disclaimer

“Cooking With Carlee” is not a dietitian or nutritionist, and any nutritional information shared is an estimate. If calorie count and other nutritional values are important to you, we recommend running the ingredients through whichever online nutritional calculator you prefer. Calories and other nutritional values can vary quite a bit depending on which brands were used.

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4.71 from 24 votes (22 ratings without comment)
Recipe Rating


Saturday 23rd of March 2024

Wow❣️ i thought nothing would ever top my go-to buttercream frosting but this is AMAZING!! Wish I could share a pic of the S’more cupcakes I just made.


Saturday 23rd of March 2024

I wish I could see them!!!


Wednesday 7th of February 2024

I ended up with 1 big oily blob, no way would it ever be spreadable


Thursday 8th of February 2024

It sounds like maybe your butter got too warm? I wonder if you could chill it for a bit and whip it again.


Monday 27th of February 2023

This is our new favorite frosting! My 3 YO grandson wanted a red velvet cake for his birthday. I used this frosting instead of cream cheese frosting. Everyone loved it. By the way, new mini marshmallow packing is 11.5 ounces. Still came out delicious.

ur mom dot com

Friday 29th of July 2022

yummy :O


Friday 19th of November 2021

What is the actual size of one serving?