Prepare the Baking Sheets:
Line two large baking sheets with waxed paper. Butter two large spoons and set them aside.

Cook the Sugar Mixture:
In a 3-quart saucepan, combine sugar, corn syrup, water, and salt. Bring to a boil, stirring frequently to dissolve the sugar. Once boiling, stop stirring and continue cooking until the syrup reaches 250°F (hard ball stage). Clip a candy thermometer to the pot, which will beep when the correct temperature is reached.

Whisk the Egg Whites:
While the syrup is cooking, whisk the egg whites in a heavy-duty mixer on high speed until very stiff peaks form.

Add Jell-O:
Once the egg whites are stiff, whisk in the Jell-O powder until fully blended.

Combine Syrup and Egg Mixture:
Once the syrup reaches 250°F, remove it from the heat. With the mixer on medium-high speed, slowly pour the syrup into the egg white and Jell-O mixture, pouring slowly over about 2 minutes.

Beat the Mixture:
Add vanilla extract and continue beating until the mixture loses its shine and holds its shape when dropped from a spoon (usually takes 4-6 minutes). If it looks too runny, continue beating for another minute or two.

Add Nuts (Optional):
Once the mixture holds its shape, mix in the chopped nuts (if using).

Form the Candies:
Use the buttered spoons to drop heaping teaspoons or tablespoons of the mixture onto the waxed paper.

Cool and Set:
Let the candies cool for at least 4 hours, preferably overnight, before storing them in an airtight container.