Bean Cassoulet with Fennel Spiced Chicken and Roasted Vegetables

Name: Bean Cassoulet with Fennel Spiced Chicken and Roasted Vegetables
Ingredients: 12 medium Brussels sprouts; 2 medium red onions; 1/2 cup extra-virgin olive oil; 3 medium parsnips; 3 medium carrots; 3 celery stalks, peeled; Finely ground sea salt; 1/4 cup Fennel Spice Rub, recipe follows; 1 (4 pound) chicken plus 2 bone-in chicken breasts; 2 to 3 garlic cloves, smashed; 1/4 pound pancetta, cut into strips about 1/2-inch thick and 1-inch long, optional; 1 pound giant white beans, such as Corona, precooked or canned with liquid; 1 cup fennel seeds; 3 tablespoons coriander seeds; 2 tablespoons white peppercorns; 3 tablespoons grey salt