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