Preheat the oven to 220C, fan-forced. Line an oven tray with baking paper. Cut the unpeeled sweet potatoes lengthwise into 1.5cm-thick wedges. Finely grate ½ tsp lemon zest, then juice half the lemon. Cut the remaining lemon into wedges. Put the chicken flat on a board, put your hand on top and halve horizontally into fillets.
Step 2 — Roast wedges
Put the sweet potato on the lined tray, drizzle with 2 tsp olive oil, season with salt and pepper and toss to coat. Roast for 25 mins or until golden and tender.
Step 3 — Crumb chicken
Meanwhile, whisk 1 egg in a shallow bowl. Combine 1 tbs flour and a pinch of salt in a shallow dish. Combine the breadcrumbs and lemon myrtle and pepperberry seasoning in a separate shallow dish. Dust the chicken with the flour, shake off the excess, then dip in the egg and coat in the breadcrumbs.
Step 4 — Cook schnitzels
Heat 1cm oil in a medium frypan over medium heat. Cook the chicken schnitzels for 2-3 mins each side until golden and cooked through. Drain on a wire rack set over paper towel (this will keep the crumb crisp).
Step 5 — Make apple salad
While the schnitzels are cooking, halve the cucumber lengthwise, scrape out the seeds using a teaspoon, then thinly slice on an angle. Slice the apple lengthwise. Stack the slices and cut into matchsticks. Combine 2 tsp olive oil and 1 tsp lemon juice in a large bowl and season with salt and pepper. Add the cucumber, apple and spinach and toss to combine.
Step 6 — Make aioli and serve
Combine the aioli, lemon zest and 1 tsp lemon juice in a bowl and season with salt and pepper. Divide the chicken schnitzels, sweet potato wedges and apple salad among plates. Serve with the lemon aioli and lemon wedges for squeezing over.