2 fennel bulbs, cut into 1/2-inch wedges, plus 2 tablespoons chopped fennel
1 onion, cut into 1/2-inch wedges
1 celery rib, thinly sliced
1 carrot, thinly sliced
4 garlic cloves, smashed
2 tablespoons tomato paste
3/4 cup dry white wine
2 cups low-sodium chicken broth
2 thyme sprigs
1 bay leaf
2 cups green olives, preferably Cerignola
Preheat the oven to 300°. In a large cast-iron casserole, heat the canola oil. Season the pork generously with salt and pepper, add it to the casserole and cook over moderately high heat, turning occasionally, until browned on all sides, about 12 minutes. Transfer the pork to a plate.
Add the fennel wedges, onion, celery, carrot and garlic to the casserole and cook over moderate heat until softened, about 5 minutes. Add the tomato paste and cook, stirring, for 2 minutes. Add the wine and bring to a boil. Add the chicken broth, thyme and bay leaf. Return the pork to the casserole and add any accumulated juices. Bring to a boil. Cover and braise in the oven for 1 hour. Remove the lid and cook the pork for 2 hours longer, adding the olives after the first hour. The pork should be very tender.
Transfer the pork to a carving board. Cover with foil and let rest for 10 minutes. Using a large spoon, skim the fat from the surface of the sauce. Discard the thyme sprigs and bay leaf. Season the sauce with salt and pepper. Slice the pork and transfer to shallow bowls. Spoon the sauce and vegetables over the pork, sprinkle with the fennel fronds and serve.
The recipe can be refrigerated overnight. Reheat gently and garnish with the fennel before serving.