Line a large baking sheet with parchment paper or a silicone baking mat. Set out a small cookie scoop or two spoons for dropping the candy. Prepare a stand mixer with the whisk attachment (or a hand mixer). Attach a candy thermometer to a medium heavy-bottomed saucepan, making sure the tip does not touch the bottom.

In the prepared saucepan, combine the granulated sugar, light corn syrup, and water. Stir gently just until the sugar is evenly moistened and combined, then stop stirring.

Place the saucepan over medium heat and bring the mixture to a boil. Cook without stirring until the candy thermometer reads 250°F (firm-ball stage), about 8–10 minutes. If sugar crystals form on the sides of the pan, gently brush them down with a damp pastry brush.

When the syrup reaches about 235–240°F, begin whipping the egg whites. In the stand mixer bowl, combine the egg whites and salt. Beat on medium-high speed until the egg whites hold stiff, glossy peaks that stand up straight when you lift the beater.

As soon as the sugar syrup reaches 250°F, remove the pan from the heat and let the bubbling subside for a few seconds.

With the mixer running on medium speed, slowly pour the hot syrup in a thin, steady stream down the side of the mixer bowl, aiming between the bowl and the whisk so it does not hit the whisk directly. Take your time; pouring too quickly can deflate the egg whites or cause splattering.

After all the syrup has been added, increase the mixer speed to medium-high and beat for 6–10 minutes, or until the mixture becomes very thick, loses its high gloss, and holds its shape like stiff marshmallow fluff. The bowl will be warm but not hot, and the candy should mound on a spoon and hold a soft peak.

Beat in the vanilla extract for about 15 seconds. Using a spatula, gently fold in the chopped pecans or walnuts until evenly distributed.

Drop a small spoonful of the mixture onto the prepared baking sheet. If it holds its shape and does not spread, it is ready. If it is still too soft or very shiny, continue beating for another minute and test again.

Working quickly, drop spoonfuls of the mixture onto the lined baking sheet, forming small mounds about 1 1/2 inches wide. A small cookie scoop works well, or use two teaspoons to scoop and push off the candy. If desired, top each piece with extra nuts, sprinkles, or crushed peppermint.

Allow the divinity to stand at room temperature for about 2 hours, or until firm and dry to the touch. The centers should remain soft and airy.

For the best texture, let the candy rest for 4–6 hours or overnight in a cool, dry place. The exterior will become delicately crisp while the inside stays marshmallow-like.