Makes: About 2½ cups
Time: About 30 minutes
Marshmallows made from scratch share only a name with the processed store-bought version. You’ll love this sweet, fluffy sauce as an accompaniment for ice cream (pages 309–315) and soft cakes. If you prefer, switch out the egg whites for 1 teaspoon gelatin powder: mix it with ½ cup water in your mixing bowl and let it bloom while you do the rest.
1. Beat the egg whites in a metal bowl with an electric mixer (fitted with the whisk attachment if you’re using a stand mixer) until frothy. Add the salt and cream of tartar and beat on high until soft peaks form. Set aside.
2. Mix together the corn syrup, sugar, and ½ cup water in a saucepan over high heat. Stir every now and then until the mixture comes to a boil, then leave it alone to cook for another 4 to 5 minutes, or until the temperature reaches 240°F.
3. Continue to beat the egg whites on medium-low speed as you slowly and carefully pour in the syrup. Increase the speed to medium and continue to beat until the mixture becomes thick and shiny. Stir in the vanilla. Stored in an airtight container, this will keep in the fridge for up to 1 week.
FLUFFY MARSHMALLOW FILLING The classic filling for whoopie pies: Beat 2 sticks butter until light and smooth. Gradually add 2 cups confectioners’ sugar and continue to beat until fluffy. Mix in 1 recipe (2½ cups) Marshmallow Sauce and an additional 1 teaspoon vanilla until combined.