Place both sausage types in a greased Dutch oven or heavy 5 quart saucepan.

Cook over moderately high heat until browned on all sides.

Remove sausages from pan and set aside.

Add olive oil to the pan drippings to equal about 4 Tbsp.

Add onions, garlic, and green beans to the pan.

Cook over moderate heat, stirring frequently, until onions are transparent and garlic is just beginning to brown.

Add basil, savory, salt, pepper, beef broth, mushrooms, and potatoes (if using), and mix well.

Return sausages to the pan.

Bring the mixture to a boil, then reduce heat to low.

Cover and simmer for about 20 minutes, or until beans and potatoes are tender.