Prepare a baking sheet by lining it with parchment paper, or a silicone mat.

Place the walnuts in a dry skillet over medium heat and stir for about 3–4 minutes until fragrant and lightly toasted, then remove and set aside.

Add the granulated sugar, butter, water, salt, and cinnamon (if using) to the same skillet and cook over medium heat, stirring occasionally, until the sugar dissolves and turns light amber, about 3–5 minutes.

Add the walnuts back in, stirring quickly to coat them evenly in the caramel. Cook for one minute.

Once the walnuts are coated in the syrup, spread them out on the prepared baking sheet, and use a spatula to separate the pieces before they harden. Let them cool completely before using.

Preheat oven to 300°F (150°C). Line a large baking sheet with parchment paper or a silicone mat.

In a large bowl, whisk together the egg white, water, and vanilla until frothy, about 1–2 minutes. Add the sugars, cinnamon, and salt, then stir to combine.

Add the walnuts and toss until evenly coated.

Spread the walnuts in a single layer on the prepared sheet without crowding.

Bake for 35–40 minutes, stirring once halfway through for halves, or every 10 minutes if using chopped walnuts.

Let cool completely on the pan. They’ll crisp up more as they cool.

Store at room temperature in an airtight container for up to 3 weeks. Avoid the fridge—moisture makes them sticky.