Preheat oven to 350° F. Lightly coat an 8-by-10-inch baking or gratin dish with 1 tablespoon of the olive oil.
In a large skillet, over medium-high heat, crumble the sausages and cook, breaking up, until golden brown, 5 to 7 minutes. Remove the sausage from skillet and set aside. Add the fennel and onion to skillet and cook until translucent, about 5 minutes. Stir in the garlic and sage and cook 1 minute more. Add the Swiss chard, a handful at a time, stirring until slightly wilted. Stir in the broth, beans, sausage, salt, and pepper. Spoon the mixture into the baking dish and set aside.
In a small bowl, stir together the bread crumbs and Parmesan with the remaining olive oil. Sprinkle the bread-crumb mixture on top and bake until golden brown and bubbly, about 30 minutes. Serve warm.
Tip: The same amount of smoked sausage may be substituted for the Italian sausage in this recipe: Slice it into rounds and chop coarsely. Great Northern beans can be substituted for the cannellini beans.