Preheat the air fryer to 200C (see Don't have an air fryer?). Cut the unpeeled potato and unpeeled sweet potato into 1.5cm-thick chips. Finely chop the capers and spring onion.
Step 2 — Air-fry chips
Put the potato, sweet potato and 2 tsp olive oil in a bowl, season with salt and pepper and toss to coat. Put in the air-fryer basket and air-fry, shaking the basket halfway, for 18-20 mins until golden and tender. Remove the chips from the air fryer and keep warm.
Step 3 — Air-fry fish
Put the crumbed fish in the air-fryer basket in a single layer. Air-fry the fish, turning halfway, for 10-12 mins until golden and cooked through. Remove from the air fryer. Bring a small saucepan of water to the boil for the peas.
Step 4 — Make sauce
While the fish is air-frying, combine the capers, half the spring onion and 2 tbs mayonnaise in a bowl and season with salt and pepper. Once the fish is cooked, return the chips to the air fryer and reheat for 2 mins or until warmed through.
Step 5 — Cook peas and serve up
While the chips are reheating, add the peas and remaining spring onion to the pan of boiling water and cook for 2 mins or until tender. Drain, then return to the pan. Add 5g butter, season with salt and pepper, then coarsely mash. Divide the crumbed fish, chips and smashed peas among plates. Serve with the sauce and enjoy!
Step 6 — Don't have an air fryer?
No worries, you can roast the chips in the oven and pan-fry the fish.