Heat 1 Tbsp olive oil in a large saucepan over medium heat. Add onions, garlic, carrots, celery, and mushrooms. Cook 10 minutes, stirring frequently. Add small amount of water, if necessary, to prevent sticking. Add remaining ingredients, except flour, 1/4 cup water and wine. Cover, reduce heat to low and simmer 30 minutes, or until vegetables are tender. Stir occasionally while cooking.
In a small bowl, gradually stir flour into 1/4 cup water until smooth. Add to stew, along with wine. Cook, stirring, 5 more minutes. Remove and discard bay leaf before serving.
