Prepare the Oven and Baking Sheet. Preheat your oven to 300°F (150°C) and line a large rimmed baking sheet with parchment paper or a silicone baking mat. This setup prevents the pecans from sliding off the pan and makes cleanup easier.

Combine the Dry Ingredients. In a small mixing bowl, mix together the brown sugar, granulated sugar, cinnamon, salt, and optional nutmeg. Break apart any lumps of brown sugar to create an even, sandy mixture.

Whisk the Egg White Mixture. In a large mixing bowl, combine the egg white, water, and vanilla extract. Whisk vigorously for 30 to 45 seconds until the mixture is pale, foamy, and bubbly.

Coat the Pecans. Add the pecan halves to the egg white mixture and stir gently until all the pecans are coated and glossy. Ensure no dry pecans remain in the bowl.

Add the Brown Sugar Coating. Sprinkle the brown sugar mixture over the wet pecans and stir gently until the nuts are evenly coated. The mixture may appear slightly grainy, which is normal.

Spread the Pecans on the Baking Sheet. Transfer the coated pecans to the prepared baking sheet, spreading them into a single layer. Make sure to separate any large clumps to allow for even toasting.

Bake the Candied Pecans. Bake the pecans for 30 to 35 minutes, stirring every 10 minutes. Watch closely during the last 10 minutes; the pecans should smell toasted, and the coating should look dry.

Cool Completely. Remove the baking sheet from the oven and use a spatula to spread the pecans apart. Allow them to cool completely on the baking sheet for about 30 minutes before serving or storing.