Pre-heat your air fryer to 325 °F (≈163 °C) while you prep the kale — this ensures crisping begins right away.

Rinse the kale leaves and use a salad spinner or paper towels to dry them thoroughly — excess moisture is the enemy of crisping.

Remove the tough central stems and tear the leaves into pieces about 2–3 inches (5–7 cm) wide. The curly leaves will curl further as they cook.

In a large mixing bowl, toss the kale pieces with the olive oil and sea salt. Massage gently so each leaf is lightly coated — you’ll smell the olive oil and feel the leaves soften under your fingers.

Add the lemon zest, grated Parmesan, black pepper (and chili flakes if using) to the bowl and toss again until the leaves are evenly coated.

Place the kale in a single layer in the air fryer basket. If your basket is small, work in two batches to avoid crowding (which causes steaming instead of crisping).

Cook for 3 minutes, then shake the basket to redistribute leaves. Cook for another 2-3 minutes or until the leaves are crisp, dry and just lightly golden at the edges. Listen for the gentle snap and watch that the vibrant green remains — you don’t want burnt brown.

Immediately remove from the fryer and transfer to a large bowl or tray. Let the chips cool for 1–2 minutes — they will crisp further as they cool. Serve right away for maximum crunch.