Baking Cakes Topping/Filling

Marshmallow Fluff Frosting (AKA 7 Minute Frosting)

Made predominantly from whipped egg whites and sugar, this marshmallow fluff frosting is an airy addition to any cake – especially if you want to spotlight the flavors inside.

Traditionally known as 7 Minute Frosting, the name is a misnomer. It takes more than 7 minutes to whip this fluffy perfection into one of my favorite frosting options. And calling it marshmallow fluff frosting is much more indicative of what it tastes like. Only it’s way better than any of the stuff that comes out of a jar (delicious though that may be) and easier to work with to frost a cake.

marshmallow fluff frosting on the outside of a cake

I discovered this classic confection about a year ago, and it’s made frequent appearances in my go-to repertoire of cake-coating options. I like it because it doesn’t require a ton of butter or powdered sugar, so it makes a frosting that’s light, and, well, tastes like marshmallow fluff. Only because it’s homemade, it’s much fresher and lighter and marshmallowy than anything store-bought.

Fair warning, though, it’s sticky as all get out. So you have to work relatively quickly to get your cake frosted and any decorative swirls in place. It works reasonably well piped onto cupcakes if you’re not too attached to definition, and/but it’s a messy frosting no matter what. For hand-held treats, there will inevitably be sticky fingers to contend with.

gloopy marshmallow fluff frosting melting off the side of the cake

Important lesson that it took me way too long to learn: you can’t use carton egg whites. I’m a little embarrassed at how many times I made this marshmallow fluff frosting (or tried to make it) using pasteurized egg whites from a carton – only to be baffled why it wasn’t maintaining its normal structural integrity. I thought maybe I’d just been impatient. Maybe I hadn’t whipped it enough. Or maybe there was something wrong with my mixer?

No. It turns out that most cartons of egg whites have a notice that reads “not suitable for whipping” or some such. (I actually learned this from a recipe that specified I couldn’t use carton whites, much to my chagrin). Something in the pasteurization process renders the chemical structure of the egg whites unsuitable for whipping into merengue. If you don’t use fresh egg whites, the result is still tasty. But it’ll also slowly gloop its way off your cake, leaving a rather messy situation… still yummy! But very messy.

Also important to keep in mind – the frosting will set within 20 minutes or so of being made, so wait until you’re ready to use it/assemble your cake before making it. It’s pretty forgiving in terms of decorative swirl/rustic look, but it won’t be malleable for very long after its made. Let you cakes cool entirely, make your fillings (if using), and then make this.

Marshmallow Fluff Frosting (AKA 7 Minute Frosting)

  • 1 1/2 cups granulated sugar
  • 2 large egg whites
  • 6 tablespoons cold water
  • 1 1/2 tablespoons light corn syrup
  • 1/4 teaspoon cream of tartar
  • pinch of salt
  • 1 teaspoon vanilla extract

Fill a medium sized saucepan with about an inch of water and heat to a simmer.

Detach the bowl from your stand mixer or get out a heat-proof bowl – you’ll be setting the bowl on top of the saucepan to heat the ingredients. In the bowl, whisk together the 1 1/2 cups sugar, 2 egg whites, 6 tablespoons cold water, 1 1/2 tablespoons light corn syrup, 1/4 teaspoon cream of tartar, and pinch of salt.

Set the bowl over the pan of simmering water, making sure the water doesn’t touch the bottom of the bowl. Heat the mixture, whisking constantly, for 5-10 minutes – until it reaches 160° F.

Remove the bowl from the heat and transfer to the stand mixer (or get out your electric hand mixer and prepare yourself for a tired arm). Using the whisk attachment on the stand mixer or the beaters on the hand mixer, whip the egg white mixture on medium speed until soft peaks form – around 5 minutes.

Then, add the 1 teaspoon vanilla and increase the speed to medium-high and continue to whip until the mixture has cooled completely (the outside of the bowl should no longer be warm to the touch). This stage will take another 5-7 minutes, so we’re looking at 10-13 minutes of whipping.

Use immediately to frost and/or fill your cake or cupcakes. The frosting will set somewhat after 20 or 30 minutes, so you’ll need to work relatively quickly to get it onto your cake.

marshmallow fluff frosting on a cake with lemon curd filling

5 comments

    1. I wouldn’t recommend leaving both out entirely – as they both help to stabilize the frosting. You can substitute, though! For the cream of tartar, you can use lemon juice instead. It helps to stabilize the egg whites and won’t really impact the flavor. For the glucose/corn syrup, it helps avoid crystallization of the sugar (when heating the mixture), so you can substitute with a number of alternate syrups: golden syrup, honey, molasses, even maple syrup. Each of those will have a small impact on flavor, but on unpleasant. Hope that helps!

      Liked by 1 person

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