Thick and flavorful Homemade Marshmallow Creme (aka Marshmallow Fluff) is easy to make. Use it for s'mores, as a frosting base for cakes and cupcakes, or as an ice cream mix-in. It's better than store bought!Adapted from King Arthur Flour
Place the egg whites and cream of tartar in the bowl of an electric mixer fitted with a whisk attachment and set aside.
In a medium saucepan, stir together the water, sugar, and corn syrup. Insert a candy thermometer and heat the mixture over medium-high heat. Don't stir the mixture as it heats so the sugar syrup doesn’t seize and become grainy.
When the sugar syrup begins to form large bubbles and the thermometer reads about 225°F, begin to beat the egg whites on high speed to soft peaks (this should take about 3 to 4 minutes). By the time the egg whites are done, the sugar syrup should be at 240°F.
Remove the syrup from the heat and, with the mixer running at medium-low speed, carefully pour it down the side of the bowl into the egg whites in a thin, steady stream. The whites will initially deflate slightly, but continue to beat and the mixture will begin to expand.
Whip for 7 to 8 minutes, until the marshmallow creme is very thick and glossy. Add the vanilla and whip for 1 more minute.
Transfer the marshmallow creme into an airtight container and store at room temperature. It will keep up to six weeks.
Cream of tartar is used to stabilize the egg whites as they're whipped into meringue. It isn't strictly necessary, but it is recommended.If desired, you can replace corn syrup with ¾ cup honey (255g).You can flavor the marshmallow cream with different extracts, Use ¼ teaspoon of almond, mint, or Fiori di Sicilia (orange vanilla). You can even add 1 to 2 tablespoons of whiskey or bourbon for a boozy twist!This recipe can be easily doubled.When it's time to clean your saucepan from the sugar syrup, the remainder left in the pan might harden into something that no amount of scrubbing will remove. In that instance, fill the pan with water and bring to a boil. That will soften the leftover syrup, and it will magically melt away with no scrubbing needed.