1/4 cup + 2 tablespoons water
3/4 cup granulated sugar
3/4 cup light corn syrup
4 liquid ounces egg whites (from about 3 large eggs)
1/2 teaspoon cream of tartar
1 1/2 teaspoons pure vanilla extract
Place the water, sugar, and corn syrup in a medium saucepan. Warm over medium-high heat until the mixture reaches 240°F on a candy thermometer, typically 10 to 15 minutes.
While the sugar is heating, beat the egg whites to soft peaks so they're ready at the same time as the sugar. Place the egg whites in the bowl of an electric mixer fitted with a whisk attachment. Beat on medium until the egg whites are foamy. Increase the speed to high, and add in the cream of tartar and salt. Continue to mix until soft peaks form.
Once the sugar mixtures reaches 240°F, carefully remove it from the heat and let rest for about 20 seconds. With the mixer running on high, slowly stream the sugar mixture into the egg whites. Continue to mix for 7 to 8 minutes, or until the outside of the mixing bowl returns to room temperature. Add in the vanilla; mix until medium-stiff peaks form.
Use immediately or store in an airtight container in the refrigerator for up to 2 weeks.