In a medium saucepan, set over medium heat, add the sugar, water, vanilla and pecans. Stir with a wooden spoon or spatula, occasionally, as it heats. It will come to a simmer, continue to cook for about 6 to 8 minutes. The pecans will be entirely covered by the transparent liquid and there will be a strong simmer.
Suddenly, the mixture will appear as if completely covered in sand: grainy and you will think you have messed it up! You have not. Continue to cook, and that clumped up sugar will begin to melt and caramelize around the already hardened and covered pecans. Stir continuously and don’t let the pecans burn. Adjust the heat if need be. You should continue until you see no more white sugar, and it is all melted and caramel covered, about 10 minutes more.
Pour the mixture onto parchment paper. Separate the pecans as you do, using a wooden spoon, or help yourself with another wooden spoon, using them as extensions of your hands. The caramel dries fast, and you will want to have the individual hardened pecans, not many clumped up. Though, nothing happens if a few clump up...
Once they have completely cooled and dried, you can store them at room temperature in a tight container.