Preheat your air fryer to 400°F.
Slice the potato into thin wedges, toss with half the avocado oil and a pinch of salt, then air fry for 15 minutes until tender.
In a medium bowl, whisk together the flour, cornstarch, baking powder, sea salt, and black pepper.
Slowly pour the cold light beer into the dry ingredients, whisking until the batter is smooth and thick.
Pat the cod fillets completely dry with paper towels to ensure the batter sticks properly.
Dip each fillet into the beer batter, allowing the excess to drip off, and place them in the air fryer basket lined with perforated parchment.
Lightly brush the battered fish with the remaining oil and air fry at 375°F for 10-12 minutes until the coating is golden and shattering-crisp.
Serve the fish and chips immediately with a fresh squeeze of lemon.