Line a baking sheet with waxed paper or parchment paper and set aside.

In a medium heavy saucepan, combine sugar, corn syrup, and water. Cook over medium heat, stirring constantly, until sugar dissolves.

Continue cooking without stirring until the mixture reaches 260°F on a candy thermometer (hard-ball stage).

While the syrup is cooking, beat the egg whites and salt with an electric mixer on high speed until stiff peaks form.

Once the syrup reaches 260°F, slowly pour it in a thin stream into the beaten egg whites while continuing to beat on high speed.

Add vanilla extract and continue beating for 4-5 minutes until the mixture holds its shape and becomes slightly dull.

Quickly fold in the nuts if using, then drop by tablespoonfuls onto the prepared baking sheet.

Set at room temperature at least 2 hours or until firm. Store airtight with waxed paper between layers.