Add the cornflour and water to a small bowl. Mix until smooth and set aside. This slurry will be used to seal the spring rolls.
Finely shred the cabbage and carrots into thin, short strips so the filling is easy to roll.
Heat 1 tablespoon oil in a wide pan over medium-high heat.
Add the shredded cabbage and carrots. Season with salt and black pepper.
Stir-fry the vegetables for 3–4 minutes, until slightly softened but not watery.
Transfer the filling to a plate and allow it to cool completely. Warm filling can soften the pastry sheets.
Place one spring roll sheet on a clean surface with one corner facing you. Keep the remaining sheets covered so they do not dry out.
Place approximately 2 tablespoons of the cooled filling near the bottom corner. Use less filling when working with smaller pastry sheets.
Fold the bottom corner firmly over the filling and roll forward once.
Fold the left and right corners towards the centre, keeping the filling enclosed.
Continue rolling tightly towards the final corner. Brush the corner with the cornflour slurry and press gently to seal.
Repeat with the remaining pastry sheets and filling. Keep the prepared spring rolls covered while assembling the rest.
Preheat the air fryer to 185°C | 365°F for 5 minutes.
Lightly brush all sides of the spring rolls with oil.
Arrange the spring rolls in the air fryer basket in a single layer, leaving a little space between each one. Cook in batches if necessary.
Air fry at 185°C | 365°F for 10 minutes.
Turn the spring rolls, brush any dry areas lightly with oil and air fry for another 6–8 minutes, until crisp and evenly golden.
Serve immediately with sweet chilli sauce, sriracha or another favourite dipping sauce.