In a large sauce pot, heat the olive oil. When the oil is hot, saut_ the onions and cabbage for about 10 minutes, or until the onions are golden and the cabbage is wilted. Season with salt and pepper. Add the sausage, garlic, bay leaves, and mustard. Saut_ for 2 minutes. Add the potatoes and chicken stock. Bring the liquid up to a boil and reduce to a simmer. Stir in the basil. Simmer the soup for 30 minutes or until the potatoes are tender. Remove the bay leaves. Adjust the seasonings if needed. Ladle the soup into a shallow bowl and garnish with chopped chives. Serve with the crusty bread.