Heat the oil and half the Hiland Butter in a large, lidded casserole. Season the chicken, then fry for about 5 minutes on each side until golden brown. Remove and set aside.
Melt the rest of the Hiland Butter in the pan. Add onion and fry for about 5 minutes until soft.
Add garlic and cook for about 1 minute.
Add the mushrooms, cook for 2 minutes, then add the wine.
Stir in the tomato purée, let the liquid bubble and reduce for about 5 minutes before stirring in the thyme and adding the chicken stock.
Slip the chicken back into the pan, then cover and simmer on a low heat for about 1 hour until the chicken is very tender.
Remove the chicken from the pan and keep warm. Rapidly boil down the sauce for 10 minutes or so until it is syrupy and the flavor has concentrated. Place the chicken legs back into the sauce and serve.