1. Prepare the Crust:

1. Line an 8×8-inch baking pan with parchment paper and lightly grease it.
2. In a saucepan, combine sugar, corn syrup, and water. Cook over medium heat, stirring until sugar dissolves. Bring to a boil and cook until the mixture reaches 250°F on a candy thermometer.
3. While the syrup cooks, beat egg whites and salt in a mixing bowl until stiff peaks form.
4. Slowly pour the hot syrup into the egg whites while continuously beating on low speed. Increase speed to high and beat until the mixture becomes thick and glossy.
5. Add vanilla extract and fold in chopped nuts or dried fruit if desired.
6. Spread the mixture evenly into the prepared pan and let it cool completely before cutting into bars.