Heat your oven to 200°C/Fan 180°C/Gas 6. Brush a baking tray with 2 tsp olive oil. Rub 1 tsp Cajun seasoning into each chicken breast. Pop on the tray. Put to one side for a few mins.
Scrub the sweet potatoes. Chop them into chips about as thick as your little finger. Toss them with 1 tbsp oil, some salt and pepper and ½ tsp Cajun seasoning. Spread them out on another baking tray.
Put the sweet potato fries in the middle of the oven and the chicken in the top. Bake for 30 mins, swapping the trays over halfway through cooking, till the chicken is cooked through and the fries are golden brown and tender.
While the chicken and chips cook, peel and coarsely grate the carrots. Finely slice the cabbage, discarding any really thick bits from the middle.
Peel and finely slice the onion. Pick the leaves off the parsley sprigs. Finely chop the sprigs. Toss all the veg in a bowl with most of the parsley.
Measure out 1 tbsp of the Dijon mustard and 1 tbsp of the brown rice wine vinegar. Tip them into a small bowl. Add ½ tbsp olive oil and some salt and pepper. Whisk together to make a dressing. Taste and adjust the seasoning.
Add the dressing to the slaw. Toss to mix. Check the chicken is cooked through by sticking a knife or skewer into the fat part of the breast. Any juices that run out should be clear. Serve with the slaw and sweet potato fries. Garnish with the parsley. Serve.