Line a baking sheet with parchment paper or wax paper. If using nuts, chop them finely and set them aside.

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

Attach a candy thermometer and cook without stirring until the mixture reaches 250°F (hard ball stage).

While the syrup is cooking, beat the egg whites in a large, clean mixing bowl until stiff peaks form.

Once the syrup reaches 250°F, slowly pour it in a thin stream into the beaten egg whites while continuously mixing at medium speed.

Be cautious and pour carefully to avoid splattering hot syrup.

Increase the mixer speed to high and continue beating until the candy loses its glossy shine and holds its shape, about 4-5 minutes.

Mix in the vanilla extract and nuts (if using) until just combined.

Using two spoons, drop spoonfuls of the mixture onto the prepared baking sheet. Work quickly as the candy will set fast.

Allow the candies to cool completely at room temperature before transferring them to an airtight container.