Preheat the air fryer: Set to 300°F (150°C). A slightly lower temperature helps prevent scorching the sugar.

Prep the basket: Lightly spray or brush the air fryer basket or tray to reduce sticking.

Whisk the coating: In a medium bowl, whisk the egg white until frothy and light, about 30–45 seconds. Stir in sugar, maple syrup (or honey), cinnamon, salt, vanilla, and optional cayenne or ginger until a thick, glossy mixture forms.

Coat the walnuts: Add walnuts and toss until every piece is evenly covered. The mixture should cling without pooling at the bottom.

Arrange in the basket: Spread walnuts in a single layer. Some touching is fine, but avoid a deep pile so they crisp evenly.

Air fry, stir, repeat: Cook for 6 minutes, then open and gently stir or shake to break up clusters. Cook another 4–6 minutes, stirring once more if needed. Total time is usually 10–12 minutes.

Watch for doneness: They’re ready when the coating looks dry and set, and the nuts are toasty and fragrant. If they still look wet, add 1–2 minutes, checking closely to avoid burning.

Cool completely: Transfer walnuts to a parchment-lined baking sheet. Spread out and let cool 20–30 minutes. The coating will harden as it cools, turning glassy and crisp.

Break and enjoy: Once fully cool, break apart any large clusters. Taste and sprinkle a pinch of extra salt if you like contrast.