PREHEAT Bring a large pot (with a lid) of salted water to the boil. BBQ grill or hot plate to medium-high (if using).
Pat chicken dry with paper towels and place in a large bowl with all remaining zingy BBQ chicken ingredients. Mix to combine and set aside to marinate for 5–10 minutes.
Cook potatoes in pot of boiling water (covered) for 13-15 minutes, until soft. Add peas for the last 3 minutes of cook time. Drain and return to pot with butter, milk and mayo (if using). Lightly crush with a fork and season to taste with salt and pepper. Set aside and keep warm, with lid on.
Heat a little oil in a large fry-pan on medium heat. Cook chicken, in 2 batches, for 4–5 minutes each side, until cooked through. Turn down heat if marinade is starting to burn. Alternatively, cook on BBQ grill or hot plate as per instructions above. Set aside on a plate, covered in foil, to rest for 2–3 minutes.
Place tomato and cucumber in a large bowl with spinach, oil and vinegar and toss to combine. Season to taste with salt and pepper.
TO SERVE place a large spoonful of smashed potato and peas on each plate. Slice zingy BBQ chicken into thick pieces and place on top of potato. Serve spinach salad on the side.
To make Cajun spice mix, combine ½ teaspoon each of garlic powder, paprika, dried oregano and dried thyme with ¼ teaspoon each ground black pepper and onion powder and a pinch of cayenne pepper.