1. For the Confit: Process salt, onion, garlic, peppercorns, parsley, and bay leaves in food processor until smooth paste with some small chunks forms, about 30 seconds, scraping down side of bowl as necessary. Massage duck legs with salt mixture and place in gallon-sized zipper-lock bag. Press out air, seal bag, and place in refrigerator 12 to 18 hours

2. For the Stew: Dissolve 2 tablespoons salt in 3 quarts cold water in large bowl or container. Add beans and soak at room temperature, 8 to 24 hours. Drain and rinse well.

3. Adjust oven rack to lower-middle position and heat oven to 300°F. Rinse duck legs under cold running water, rubbing off any salt mixture. Pat legs dry with paper towels. Heat duck fat in large saucepan over medium heat until completely transparent (if using canola oil, it should register about 135°F on instant-read thermometer). Add duck legs, making sure they are completely submerged in fat. Transfer pot to oven and cook until meat offers no resistance when poked with fork, 3 to 4 hours.

4. Using kitchen twine, tie together celery, bay leaf, and thyme, and set aside. Place sausage and salt pork in medium saucepan and add cold water to cover by 1 inch; bring to boil over high heat. Reduce heat to simmer and cook 5 minutes. Transfer sausages to cutting board, allow to cool slightly, then cut into 1-inch pieces. Remove salt pork from water; set aside.

5. Heat 2 tablespoons oil in 8-quart Dutch oven over medium-high heat until beginning to smoke. Add sausage pieces and brown on all sides, 8 to 12 minutes total. Transfer to medium bowl. Add pork shoulder and brown on all sides, 8 to 12 minutes. Add onion and carrots; cook, stirring constantly, until onion is translucent, about 2 minutes. Add garlic and tomato paste and cook, stirring constantly, until fragrant, 30 seconds. Return sausage to Dutch oven; add white wine, using wooden spoon to scrape browned bits from bottom of pan. Cook until slightly reduced, about 30 seconds. Stir in diced tomatoes, celery bundle, and reserved salt pork.

6. Stir in broth and beans, pressing beans into even layer. If any beans are completely exposed, add up to 1 cup water to submerge (beans may still break surface of liquid). Increase heat to high and bring to simmer. Cover pot, transfer to oven, and cook until beans are tender, about 1 1/2 hours.

7. Remove confit and stew from oven and increase temperature to 350°F. Using slotted spoon, transfer duck legs to large plate and cool slightly. Once cool enough to handle, remove skin from duck legs and discard. Remove meat from bones, leaving meat in large pieces; discard bones. Meanwhile, remove celery bundle and salt pork from bean stew and discard. (Alternatively, dice salt pork and return to stew.) Using large spoon or ladle, skim fat from surface of stew and discard. Adjust seasoning of stew with salt and pepper. Add duck meat and stir gently to combine. Bake, uncovered, for 20 minutes.

8. Meanwhile, pulse bread and remaining 2 tablespoons oil in food processor until crumbs are no larger than 1/8 inch eight to ten 1-second pulses. Transfer to medium bowl, add parsley, and toss to combine. Season to taste with salt and pepper.

9. Sprinkle 1/2 cup breadcrumb mixture evenly over casserole; bake, covered, 15 minutes. Remove lid and bake 15 minutes longer. Sprinkle remaining breadcrumb mixture over top of casserole and bake until topping is golden brown and beans are bubbling around edges of pot, about 30 minutes. Let rest 15 minutes before serving.

Serves 8 to 10