To make an easy marshmallow fluff, combine 3 egg whites, 2 cups light corn syrup and 1/2 teaspoon salt in a large bowl. Beat the ingredients for 10 minutes, until thick. Add 2 cups of confectioner's sugar and 1 tablespoon of vanilla. Beat on low speed until glossy.
Alternatively, mix together 3/4 cup granulated sugar, 1/2 cup light corn syrup, 1/4 cup water and 1/8 teaspoon fine salt in a saucepan and bring to a boil. Stirring occasionally, check the temperature of the syrup with a candy thermometer until it reaches 240 degrees Fahrenheit.
Place 2 large egg whites and 1/4 teaspoon of cream of tartar in a stand mixer fitted with a whisk attachment. Whip the egg whites on medium speed until they reach soft peaks. Reduce the mixer speed to low, and drizzle about 2 tablespoons of syrup into the egg whites, making sure not to raise the temperature of the egg whites too quickly. Drizzle the rest of the syrup slowly into the egg whites, and increase the mixer speed to medium high.
Whip the mixture for about seven minutes, until the marshmallow fluff is glossy and somewhat stiff. Add 1 1/2 teaspoons pure vanilla, and whip the mixture again for two minutes. This recipe makes 2 1/2 cups of marshmallow fluff, which may be stored in the refrigerator for up to two weeks.