Preheat oven to 300°F and line a baking sheet with parchment paper. In a bowl, whisk 1 egg white with 1/2 tbsp water and 1/2 tsp vanilla until frothy.
In another bowl, mix 3 cups walnuts with 1/4 cup each white sugar and brown sugar, 1 tsp cinnamon and 1/4 tsp of cloves, nutmeg and ginger.
Toss the walnut mixture in the egg white mixture; transfer to the sugar mixture and toss until covered.
Spread walnuts evenly on a baking sheet and sprinkle with 1 tsp fleur de sel. Bake for 25 to 30 minutes, stirring at least once. Let cool before transferring to an airtight container. (They can be stored for up to 2 weeks.)