Heat the oil in a large saucepan over medium heat. Cook the sausage, turning occasionally, until browned and cooked through, about 10 minutes. Transfer to a cutting board and let rest at least 5 minutes before slicing.
Add the onions to the pan and cook over medium heat, stirring occasionally, until soft, about 6 minutes. Add the garlic and cook, stirring, for 1 minute. Add the wine and broth and bring to a boil. Add the beans, escarole, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring occasionally, until the escarole wilts, about 3 minutes.
Spoon into individual bowls and top with the Parmesan. Serve with the sausage and crusty bread, if desired.
Substitution: If you are unable to find escarole, a slightly peppery relative of endive with sturdy light green leaves, try using Swiss chard or spinach.