Preheat the oven to 200°C, fan 180°C, gas mark 6. Season the chicken breasts with a pinch of salt and pepper, place on a baking tray and cook for 15 minutes or until cooked through.
Meanwhile, boil the potatoes for 20 minutes, or until tender.
Whilst the potatoes are cooking, put the red onions in a small bowl and cover with the red wine vinegar. Leave to marinate for 30 minutes.
Once the chicken and the potatoes are cooked, allow to cool, then slice the chicken thinly and cut the potatoes in half lengthways.
Drain the red onions and reserve the vinegar.
Mix the onions with the potatoes, sweetcorn, salad leaves, cucumber and two-thirds of the parmesan. Dress the salad with the olive oil and 1 teaspoon of the red wine vinegar marinade.
Evenly sprinkle over the remaining parmesan and grated carrot to serve.