Begin by measuring out all your ingredients. Having everything ready makes the process smoother and more enjoyable.
In a medium saucepan, combine the sugar, light corn syrup, salt, and water. Stir gently until the sugar is dissolved, then bring the mixture to a boil over medium heat. Use a candy thermometer to monitor the temperature, aiming for about 240°F (soft-ball stage).
While the syrup is cooking, place the egg whites in the bowl of your stand mixer (or a mixing bowl if you're using a hand mixer). Beat on medium speed until soft peaks form. This usually takes about 3-5 minutes.
Once the syrup reaches the desired temperature, carefully pour it in a thin stream into the whipped egg whites while the mixer is running on medium speed. Be sure to avoid the whisk to prevent splattering.
Continue beating the mixture on high speed until it cools down and forms stiff peaks. This process typically takes about 5-7 minutes. Add the clear vanilla extract and beat for an additional minute to incorporate.
Once your Marshmallow Frosting is ready, use a spatula or piping bag to decorate your cakes or cupcakes. The glossy finish will make your treats look absolutely stunning!
