Clean and cut the onion in rings. Pour the olive oil in a saucepan and add the onion and the chicken. Cook on high heat. When the chicken is golden brown, turn the heat down and add the flour, the bacon, water, white wine and the gravy cubes. Let them cook. Turn the chicken now and then, pouring the juices all over it. Add the mushrooms 15 minutes before the end. Take the chicken out of the pan and place in a deep dish with its juices.