In a 3 1/2 -or 4-quart crockery cooker place mushrooms and onions. Stir in the 1/2 cup broth, the wine, tomato paste, garlic salt, rosemary, thyme, pepper, and bay leaf. Add chicken.
Cover and cook on low-heat setting for 7 to 8 hours or on high-heat setting for 3 1/2 to 4 hours.
Transfer chicken to a serving platter. Cover chicken and keep warm. For sauce, transfer vegetables and cooking liquid to a medium saucepan. In a small bowl combine the 1/4 cup broth and the flour; stir into mixture in saucepan. Cook and stir until thickened and bubbly; cook and stir for 1 minute more. Remove and discard bay leaf. Spoon some of the sauce over chicken. Pass remaining sauce. If desired, serve with mashed potatoes and sprinkle with parsley.