Preheat oven to 250F and line a cookie sheet with parchment paper.
Combine egg white, water and vanilla in a large bowl and whisk vigorously for 30 seconds (mixture should be foamy/frothy).
Add walnuts and stir until all walnuts are coated in egg white.
In a separate bowl, whisk together the sugars, cinnamon, and salt.
Pour the sugar mixture over the walnuts and stir until completely combined.
Spread nuts in an even layer onto prepared cookie sheet.
Bake on 250f for 45-50 minutes, removing cookie sheet from oven every 15 minutes and using a spatula to stir/flip the walnuts (be sure to stir ALL of the sugar mixture as well, or it may burn to the pan).
Candied walnuts are done when they appear dry and there is no liquid left on the nuts or on the pan.
After baking, allow to cool at least 15 minutes before enjoying.
Store uneaten candied walnuts in an airtight container at room temperature.
You may substitute other nuts for the walnuts. Almonds, pecans, and cashews all work well.