1. Preheat the oven to 180°C/356°F/gas mark 3.
2. Saute the onion in a large ovenproof pan with the oil until soft.
3. Add the carrots and stir. Cook for 4-5 mins.
4. Toss the chicken in the flour, add to the pan and cook until lightly browned.
5. Then add the potatoes, thyme and stock.
6. Heat until simmering, cover and cook in the oven for 45 mins.
7. Mix the cornflour with 5tbsp of water to make a paste.
Stir into the casserole and then add the peas and cook for another 10 mins.