Mix the melted butter with the maple syrup, cinnamon and salt in a mixing bowl. Add the walnuts and toss until well coated, then sprinkle with sesame seeds.

Set the air-fryer to 160°C using the ‘Roast’ mode and transfer the coated nuts to the fryer basket. Roast for 6 minutes, giving the basket a shake halfway through.

Tip the walnuts onto a sheet of greaseproof paper and spread them out into a single layer. Leave to cool completely before serving or storing in an air-tight container.