Preheat oven to 300 degrees F. Line a large baking sheet with parchment paper.: You will notice the oven begin to breathe warm air and the parchment gives a neutral surface that prevents sticking. Heating to 300 degrees F ensures the sugars crisp slowly without burning, producing an even, glossy coating. A common mistake is using too high heat which scorches the sugars before the pecans toast properly, so resist the urge to crank the temperature.
Wet coating: in a mixing bowl beat egg white, vanilla, and water until stiff peaks form.: in a mixing bowl beat egg white, vanilla, and water until stiff peaks form. : As you whip the mixture, it transitions from glossy foam to defined peaks that hold shape, and the echo of the whisk lightens. This airy texture is what helps the sugar cling uniformly. Watch for overbeating, which can make the foam dry and less adhesive; stop when peaks stand tall but still look moist.
Dry coating: Add granulated sugar, brown sugar, cinnamon, and salt to a bowl and stir to combine.: Add granulated sugar, brown sugar, cinnamon, and salt to a bowl and stir to combine. : When you stir these dry ingredients, a fragrant cloud of cinnamon will rise and the sugars will look uniformly speckled. Mixing ensures every pecan will meet a balanced blend of sweet and spice. Avoid lumps by giving the mixture a quick sift or vigorous stir; clumps will create uneven spots on the nuts.
Add pecans to the egg whites mixture and gently toss to coat. Add the cinnamon sugar mixture and stir gently until the pecans are well coated.: As you fold the pecans into the foam, they become glossy and tacky, the coat clinging like a thin shell. When you add the sugar mix, it should dust the nuts evenly and begin to stick. If the nuts look patchy, toss more gently to avoid breaking the halves, and be careful not to overwork the coating which can knock sugar off instead of adhering it.
Bake: Spread the pecans into a single layer on the prepared baking sheet. Bake for about 40-45 minutes, stirring every 15 minutes. Remove from the oven and allow the pecans to cool completely on the baking sheet.: Spread the pecans into a single layer on the prepared baking sheet. Bake for about 40-45 minutes, stirring every 15 minutes. Remove from the oven and allow the pecans to cool completely on the baking sheet. : During baking you will hear a soft sizzle as moisture leaves and the sugar begins to set, and the aroma of cinnamon and toasted nuts will intensify. Stirring every 15 minutes ensures even browning and prevents hot spots, and you will see the coating become drier and sandier as it approaches readiness. One easy error is skipping the stirring which can lead to burned clusters on the sheet; keep an eye on color for a golden, not dark brown, finish. Cooling on the pan lets the coating harden; moving them too soon can smear the glaze.
Store candied pecans in an airtight container at room temperature or in the refrigerator for several weeks.: Once cooled, the pecans should make a crisp clack when tapped together, indicating the coating set properly. Store them sealed to maintain crunch and keep odors out. Condensation can soften the coating, so avoid refrigerating warm nuts or transferring them between temperature extremes without sealing; moisture is the main culprit if they lose their shine.