Chop the chicken thighs into small pieces about 2-3 cm wide (1 inch).
On a separate board, peel and chop the carrots, sweet potatoes and parsnips into chunks. Dice the white part of the leeks and then also chop the celery, green beans and new potatoes. Crush the garlic cloves.
In a frying pan heat 1 tablespoon olive oil. Coat the chopped chicken thigh pieces in flour and cook them on both sides until browned. Remove onto a plate and set aside.
In the same pan, add the second tablespoon olive oil and cook the garlic, leeks, carrots, celery and thyme leaves for a few minutes.
Roll the pieces of sweet potatoes, parsnips, and new potatoes around in the flour until coated. Add to the frying pan and cook for a few minutes.
Transfer all the vegetables to an oven proof casserole and add in the chicken pieces. Sprinkle on the rest of the flour.
Pour in the stock and green beans and bring to the boil.
Cover and cook for 1 hour on a low heat on the hob, or move to the oven and cook at 180°C (or 350°F) for 50 minutes – 1 hour. Check the liquid level every now and then and top up with water if necessary.
If you’re using a slow cooker, you can cook it on high setting for 4 hours or on a low setting for 8 hours.
Serve with steamed greens and crusty bread.