Preheat oven to 160°C (325°F). Heat the olive oil in a pan and brown the chicken, skin side down until nice and crisp. Arrange the chicken, skin side up in an oven proof baking dish.
Sprinkle the chicken with the salt and smoked paprika. Cover and bake for 30 minutes.
While the chicken is in the oven, prepare the sauce by adding the onion and red pepper to the pan drippings and sauté until soft. Add the mushrooms, thyme and a little extra oil if necessary and stir fry until soft.Sprinkle in the flour and stir through to mix well .Add the chicken stock, red wine, tomato paste, salt, sugar and Worcestershire sauce and stir until thickened.
When the chicken is done, uncover and pour off any excess fat. Pour the sauce over and add the onions to the dish.