Heat the oil in a casserole over a medium heat and add the butter. Colour the skin-side of the thighs for five minutes then add the breasts to the pan and brown them together with the thighs for another five minutes until well-browned. Take the guinea fowl out of the pan and set aside.
Add the shallots to the casserole and cook gently for 5-10 minutes to brown them, then remove from the pan and set aside.
Add the onions to the pan and fry to brown them. Return the shallots and guinea fowl to the pan. Add the white wine, chicken stock and thyme, put a lid on and simmer over a low heat for 20 minutes until the juices of the meat run clear when pierced with a fork. Season to taste with salt and pepper.
Garnish with parsley and thyme and serve.