Add vegetable oil to large saucepan over medium heat. Add sausage and cook until lightly browned, about 8 minutes. (If using leftovers, add them 5 to 10 minutes before serving so they are heated through.) Add chicken and cook until lightly browned, about 3 to 4 minutes. Stir constantly. Add chopped onion, bell pepper and celery. After 3 to 4 minutes, add spice mix and garlic. Stir, scraping the bottom of the pan. Add rice and chicken stock. Cook, uncovered, until stock is absorbed and rice is tender. Remove bay leaves. To make Spice Mix: Combine bay leaves, salt, cayenne, white pepper, black pepper and dried thyme.