Preheat oven to 160°C (140°C fan-forced). Make a bouquet garni by tying the bay leaf, thyme and parsley together with kitchen string; set aside. Toss the chicken in seasoned flour until well coated; shake away excess flour.

Heat 2 teaspoons of the oil over medium-high heat in a large casserole dish. Cook half the chicken until browned all over. Remove from dish. Repeat with another 2 teaspoons of oil and the remaining chicken. Add the remaining oil to the same pan and cook the leeks over medium heat for 2 minutes or until softened slightly but not browned. Add the garlic and cook stirring for 1 minute until aromatic.

Add the wine and bring to the boil. Cook, stirring until reduced by about half.

Return the chicken with any juices to the dish; add the bouquet garni, stock, potatoes and mushrooms, and stir to combine. Bring to the boil. Cover and place in the oven for 1 hour or until chicken is very tender. Stir through the mustard, cream, peas and parsley. Cover and stand for 5 minutes. Remove bouquet garni.