Creamy and super smooth, this buttercream brings chocolate and marshmallow together in the perfect balance. It’s ideal on chocolate cake to create either a s’mores or chocolate covered marshmallow flavor. Or—my favorite—use it with a milk chocolate sponge to create a hot chocolate cake, just in time for the holidays.

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Post Update: you can make this using your own marshmallow fluff! This recipe will make the equivalent of two 7oz jars of fluff, so use half of it to make a single batch of chocolate marshmallow buttercream.

Have you ever had a Scotchmallow? See’s Candy sells them, and they’re half caramel, half marshmallow, all dipped in chocolate. They’re a lot like the chocolate caramel dipped marshmallow sticks sold at Disneyland—which are for sure in my top three Disney desserts along with Gibson Girl ice cream and churros. And now I’m sad that Disneyland is closed and genuinely worried about it ever being the same.

Okay, before I get too off track about my love for Disneyland, Scotchmallows (and the Disneyland dipped marshmallows) inspired one of my best cakes last year. I made a chocolate cake with marshmallow buttercream and homemade caramel filling and frosted the whole thing in this chocolate marshmallow buttercream. It was a whim—adding some chocolate ganache to the remaining marshmallow buttercream after I filled and crumb coated the cake.

Best decision ever.

What resulted was a fluffy, creamy, very smooth, and lightly chocolate-y frosting. The trick is only adding a small amount of ganache so that the flavors complement each other without overpowering each other.

How to make chocolate marshmallow buttercream

This is slightly more steps than plain buttercream, but nothing is complicated and it’s worth the extra five minutes. First, mix heavy cream and chocolate (chips, chunks, baking—whatever you prefer) in a heatproof bowl.

Set it over a saucepan with already simmering water. Turn it down to low or medium low, whatever keeps the water simmering. Avoid using too small or too large a pan—you want the ganache to all be exposed to the heat. Stir the mixture constantly, until almost all the chocolate is melted. Remove from heat and stir well until smooth. Set aside to cool. (see note about using less cream if needed)

Cream your butter.

Add in about half the sugar and mix on low, slowly increasing speed to high to avoid sugar flying everywhere. Beat until smooth, about 30 seconds. Scrape down the bowl with a rubber spatula then add the marshmallow (homemade or store bought) and beat on high until smooth, about 30 seconds. Scrape the bowl again (notice a trend here? My least favorite but very important step). Add the rest of the sugar and again start on low then increase speed to high until smooth.

Scrape the bowl again then add the vanilla and salt and beat just to combine.

Add about 3/4 of the chocolate and beat on high until fully blended. Taste and add more chocolate as needed. You don’t want to overpower the marshmallow flavor. Scrape down the bowl and beat on high for 2 minutes to fluff it up then stir vigorously for 1 minute with a wooden spoon or rubber spatula to release any air bubbles.

If you’re making a tall cake, chill the frosting for about 10 minutes before using so it’s a little more firm and better able to support all those layers.

Enjoy!

Tips for this recipe

Use cocoa powder or plain melted chocolate if the cake will be outside

The ganache makes this a really smooth, fluffy frosting, but it’s not going to hold up well in hot weather. You can fix this one of two ways. First, you can very carefully melted chocolate with little to no cream following the same steps as I used for the ganache. Then, stir it frequently as it cools to keep it pliable, and be sure to add it to the frosting as soon as it reaches room temperature and before it hardens again.

The other option is to use cocoa powder, but the taste will be different. Most baking cocoa is unsweetened and has a different chocolate flavor than chocolate chips, but I can assure you it still tastes great! This option will also be the least likely to melt in high heat or prolonged direct sunlight. It’s best to start with just a couple tablespoons (sifted) and go from there. I like about 4, while some people like just 2 or 3.

Don’t melt all the chocolate over the double boiler

Whether you’re sticking with my recipe or using less or no cream, you don’t want to cook the chocolate to smooth over heat. Baking chocolate is the most likely to melt smoothly, but each brand of chips and chunks is made a little differently. If you keep it over the heat until it’s perfectly smooth, you’ll likely never reach the desired consistency. You’ll go from fully melted to separated and grainy without realizing it. It’s best to remove the bowl from the heat when the chips or chunks or baking bar pieces are about 75% melted. You can return it to the heat if you pulled it too early, but you can’t really recover if you heat the ganache too long.

Double the recipe for larger cakes

This doesn’t make quite as much as some of my other frostings, so if you plan to make a large cake or want to do several layers, it’s best to increase the recipe. If you can find a 10 ounce jar of marshmallow fluff, you can do a one-and-a-half batch—just multiply all the ingredients by 1.5. However, I find it’s easiest to just get two jars of fluff, double the recipe, and save the extras for later.

Make your own marshmallow!

This one is SO easy. Yes, it does take about 20 minutes, but I never knew how easy it was to make marshmallow fluff that actually is fluffy. This recipe makes about 4 cups, or double what you’d need for this chocolate marshmallow buttercream. You can use more, to taste, or use it to make a double recipe and freeze the extras. Or, just make a full batch of marshmallow fluff and eat the leftovers on ice cream or with a spoon. No judgment here!

My buttercream tools

Here are my must-have tools I use for making this buttercream. Affiliate links provided.

Stand mixer or handheld mixer

1M piping tips

Reusable silicone piping bags

Large and small offset spatulas

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Chocolate Marshmallow Buttercream

total time: 15-20 minutes

Print recipe

Servings: about 3 cups, enough to frost a two-layer 8” or 9” cake, or 24 cupcakes

Ingredients:

4 ounces chopped baking chocolate or chocolate chips (see note)
3 ounces heavy whipping cream
1 cup (2 sticks) unsalted, European style butter, room temperature but still firm
3 cups powdered sugar
½ batch marshmallow fluff (or one 7oz jar store bought marshmallow cream)
¼ teaspoon sea salt
½ tablespoon vanilla extract (optional, enhances the marshmallow flavor)

Instructions:

If using homemade marshmallow fluff, make that first. You can immediately start on the buttercream once the fluff is done.
Make the ganache. Combine the chocolate and heavy cream in a heatproof bowl. (See note about using just chocolate to make a sturdier frosting. This will hold up fine indoors but may get fairly soft in direct sunlight or summer heat). Bring 1-2” water to a boil in a small to medium saucepan that can hold the bowl on top in such a way that all or almost all of the ingredients are over the water and not over the stove. Once the water boils, turn down the heat to medium low or low and place the bowl over it. You want it to stay simmering without getting too hot. Stir constantly with a rubber spatula until the chocolate is mostly melted. Remove from heat and stir or whisk vigorously until it is all melted and smooth. Return to heat if some chunks remain, but don’t worry if the color looks a little streaky (usually only noticeable in a glass bowl). It’s best not to overheat the chocolate because it will become grainy and separated. Set aside to cool slightly, about 20 minutes.
In the bowl of your stand mixer fitted with the paddle attachment or in a large mixing bowl using your hand mixer, cream butter on high until smooth, about 1 minute.
Scrape the bowl with a rubber spatula then add in about half of the powdered sugar. Blend on low then slowly increase speed to high and mix until smooth before adding more. Scrape the bowl then add in the marshmallow fluff. Mix on high until well-blended, about 30 seconds. Add the rest of the sugar and again beat on low then increase slowly to high for about 30 seconds or until smooth. Add salt and vanilla, if using, and blend until fully incorporated.
Add in about ¾ of the cooled ganache and beat on low for a few seconds then increase speed to high until smooth. Stop and scrape the bowl. Taste to see if you need more powdered sugar or more chocolate. I used almost all of my chocolate and no extra powdered sugar and it was perfect. If it’s sweet enough but not holding its shape like in the photos, you can fix this with some refrigeration. If it’s too stiff or grainy, try beating it on high a little longer or, as a last resort, mix in heavy cream one tiny splash at a time until smooth.
Once taste and texture are to your liking, scrape the bowl then mix on high for 2 minutes, until smooth and fluffy then stir by hand with a wooden spoon or rubber spatula for 1 minutes to release any large air bubbles that formed.

Frost cake or cupcakes and enjoy! Frosting can be stored in the fridge in an airtight container for 1-2 weeks or in the freezer for 1-2 months. To use chilled frosting, let come to room temperature then whip for about a minute to fluff back up.