In a nonstick skillet over medium high heat, melt together brown sugar and water until rapidly bubbling. Add pecans, stirring thoroughly to coat. Cook, stirring, for 3-4 minutes, until fragrant and most of the liquid has evaporated. (But not so long at the sugars burn.)
Spread pecans into a single layer onto a parchment-lined baking sheet, and use a fork to separate them. Let stand at room temperature for about an hour, until fully cooled, set, and dry. (Pecans will be only very slightly tacky to the touch.)
Break apart any pecan clusters and store in an airtight container at room temperature for up to a week, in the refrigerator for a couple of weeks, or in the freezer for up to 2 months.
Cinnamon Caramelized Pecans: Add 1/4 teaspoon cinnamon to the pan with the brown sugar.
Spicy Caramelized Pecans: Add 1/4 teaspoon (or more or less, to taste) cayenne pepper to the pan with the brown sugar.
Salted Caramelized Pecans: Sprinkle the pecans with flaked sea salt after you transfer them to the baking sheet to cool.