Put beans into a large bowl, cover with water and set aside to let soak for 8 to 12 hours; drain.

Transfer beans to a medium oven-proof pot and add enough water to cover by 2 inches.

Stud onion with cloves and add to pot.

Stir in thyme, bay leaves, celery and one of the carrots.

Reduce heat to medium-low and simmer, covered, about 45 minutes, or until beans start to become tender.

Discard onion, celery, carrot, thyme and bay leaf and stir in salt and pepper.

Meanwhile, preheat oven to 425°F.

Combine remaining 4 carrots, parsnips, celery root, leeks and oil on a large rimmed baking sheet.

Roast, stirring occasionally, until nearly tender, about 45 minutes.

Transfer roasted vegetables to pot with beans and add additional water to cover, if needed.

Simmer until beans and vegetables are tender, about 15 minutes more.

Pour off excess liquid, leaving just enough so that vegetable and bean mixture is stew-like.

While stew is simmering, reduce oven temperature to 400°F.

Place breadcrumbs on a large rimmed baking sheet and toast about 8 minutes or until lightly golden, stirring once.

Sprinkle bread crumbs evenly over surface of stew.

Transfer stew to oven and bake, uncovered, until bread crumbs are golden brown, 10 to 12 minutes.

Ladle into bowls and serve.