Place the beans in a bowl and soak in boiling water. Set aside.
Cook the bacon over medium heat until crisp and remove. crumble when cool and set aside.
Add the onions and garlic to the bacon fat and sauté until softened, about 3-4 minutes.
Add the duck legs, cover with water, cover and simmer for 2-3 hours, or until duck is tender and easily comes off the bone.
Remove duck from stock and let cool. Shred and reserve bones for making stock in the future.
Pour the cooking liquid in a heat proof bowl and set aside.
Add the leeks to the pot with the duck fat and sauté over medium heat for 3-4 minutes, until softened.
Drain the beans.
Add the shredded meat, beans, potatoes, crumbled bacon, all seasonings and the reserved cooking liquid back to the pot.
Bring to a simmer, cover and cook for 50-60 minutes, or until beans are tender.
Stir in the spinach and cook 2-3 minutes. Add additional salt to taste if needed.
Remove from heat and serve with crusty bread.