Line baking sheets with parchment paper and grease 2 spoons with non-stick cooking spray. Set aside
In a saucepan over medium-low heat, cook the sugar, corn syrup, and water, stirring constantly until all the sugar is dissolved and the mixture comes to a boil.
Insert your candy thermometer. Continue cooking, without stirring, until the mixture reaches 260℉ (hard ball stage).
Meanwhile, in the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on medium-high speed until stiff peaks form.
Once the hot sugar mixture reaches 260℉, remove from heat. With the mixer on medium speed, carefully and very slowly mix the hot sugar syrup into the egg whites, pouring in a thin stream. Add vanilla extract.
Increase to high speed and continue to mix for 5-10 minutes, or until the mixture holds its shape and loses its gloss. Do not over mix.
Gently fold in the pecans.
Quickly drop dollops of the mixture on the lined pans. Use one spoon to scrape the mixture off the other spoon. Optional: Top each with a pecan halve.
Allow to set at room temperature overnight, or until the candies are dry and firm.
Notes
Store in an airtight container at room temperature for up to one week.