Season all the chicken with salt and pepper.
Put a large frying pan over medium flame with the oil, then cook the chicken untl browned in it for about 8 minutes a side. Take out of the pan and leave aside for now.
Sauté the mushrooms, garlic and onion in the same pan for around 5 minutes or until they soften up.
Rejoin the chicken with them into the pan and add in all the rest of the ingredients. Cover partially and cook on low for 60 minutes.