01 -
In a heavy-bottom saucepan fitted with a candy thermometer, combine water, granulated sugar, and light corn syrup. Set over medium-high heat without stirring. Allow the mixture to bubble, heating until it reaches 115°C.
02 -
While the syrup heats, add egg whites and cream of tartar to a stand mixer bowl fitted with a whisk attachment, or a large bowl using an electric hand mixer. Beat until soft peaks form, about 3 to 4 minutes.
03 -
When the sugar syrup reaches 115°C, remove from heat. With the mixer running on medium speed, carefully and gradually pour the hot syrup into the whipped egg whites in a slow, steady stream.
04 -
Increase mixer speed to medium-high and continue beating. The mixture will deflate initially, then thicken. Beat for an additional 7 to 8 minutes until glossy and stiff.
05 -
Whisk in the vanilla extract. Let the marshmallow fluff cool completely. Transfer to an airtight container and store at room temperature for up to two weeks.