In a large dutch oven or soup pot, heat the oil over medium heat. Add the sausage and cook until the sausage is browned. Once the sausage is cooked, tilt the pan to one side and use a paper towel to sop up and discard any excess oil.
Add the chicken broth and remaining ingredients (excluding the bread crumbs) to the pot. Bring to a boil.
Reduce heat to low, cover, and simmer the mixture, stirring occasionally for 45 minutes to 1 hour, or until the vegetables are tender.
Meanwhile, make the breadcrumb topping. In a mixing bowl, combine garlic, bread crumbs, parsley, cheese, and butter. Set aside.
Preheat the oven to 400 degrees. Spread the crumb mixture over the cassoulet in the dutch oven or transfer it to an oven safe casserole dish. Bake for 10-15 minutes or until crumbs are golden brown and crisped.
If you'd like to make this dish ahead of time, prepare it without the crumb topping. Cover tightly and refrigerate for 2 days or freeze up to 4 months. When ready to cook, uncover the cassoulet, sprinkle it with the breadcrumbs, and bake 45 minutes to 1 hour at 400 degrees.