Preheat the air fryer to 200C (see cooking tip). Cut the unpeeled sweet potatoes into 2cm-thick rounds. Halve the cucumber lengthwise, then thinly slice. Thinly slice the cabbage with a sharp knife or mandoline. Thinly slice the spring onion on an angle.
Step 2 — Pickle slaw
Combine 1 tbs white wine vinegar and 1½ tsp sugar in a large bowl and season with salt. Add the cucumber and cabbage and toss to coat. Set aside to pickle, tossing occasionally, until needed.
Step 3 — Air-fry sweet potato
Generously spray the sweet potato with olive oil and put in the air-fryer basket. Air-fry the sweet potato, tossing halfway, for 13-15 mins until golden and tender. Remove from the air fryer.
Step 4 — Crumb chicken
Meanwhile, cut the chicken into 3cm chunks and season with salt and pepper. Combine the maple and mustard dressing and three-quarters of the lemon myrtle seasoning in a shallow dish. Put the breadcrumbs in a separate shallow dish. Dip the chicken in the maple and mustard mixture, then coat in breadcrumbs and shake off the excess.
Step 5 — Air-fry chicken
Generously spray both sides of the crumbed chicken with olive oil and put in the air-fryer basket, in batches if necessary (it's important not to overcrowd the basket, otherwise the hot air won't have room to circulate, which is what makes the chicken extra crispy). Air-fry the chicken, turning halfway, for 8 mins or until golden and cooked through. Remove from the air fryer.
Step 6 — Make aioli and serve
Return the sweet potato to the air-fryer basket and air-fry for 1-2 mins until warmed through. Combine the aioli and remaining lemon myrtle seasoning in a bowl. Taste, then season with salt. Divide the popcorn chicken, roast sweet potato and pickled slaw among plates. Scatter with the spring onion and serve with the lemon myrtle aioli.