Preheat your air fryer to 400°F (200°C).
Slice the Russet potato into even wedges and pat them dry with a paper towel.
In a bowl, toss the potato wedges with 0.5 tablespoons of avocado oil, sea salt, and black pepper.
Place the wedges in the air fryer basket and cook for 15-18 minutes, shaking halfway through, until they are tender and browned.
While the potatoes cook, pat the cod fillets dry and cut them into large strips.
In a shallow bowl, whisk together the arrowroot powder, egg white, and light beer until a smooth, thin batter forms.
Lightly grease the air fryer rack with the remaining avocado oil.
Dip each piece of cod into the batter, allowing the excess to drip off, and place it in the air fryer basket (do not overlap).
Air fry the fish at 400°F for 8-10 minutes, flipping once, until the coating is golden and the fish flakes easily.
Serve the fish and chips hot, garnished with fresh parsley and a squeeze of lemon juice.