Preheat the oven to 350 degrees.
In a 5 ½ quart (or larger) pot or French/Dutch oven, liquefy the duck fat at medium heat.
Add chicken thighs skin down in the bottom of the pan. Allow to cook for 8 minutes on Medium to Medium High, periodically checking to be sure the skin is not sticking to the pan (if it is gently slide a heat-proof spatula underneath to free the skin).
Using heatproof tongs, turn the chicken thighs over and cook for an additional 3 minutes. Remove from pan to a plate; set aside.
Add the sausages to the same pan (be careful of hot fat splattering!) and cook until lightly browned on each side (approximately 3-4 minutes total). Remove and set aside (can be added to the plate with the chicken)
Add the bacon to the pan. Sauté to render the fat only (about 3 minutes). NOTE: The fat will turn a gray color and be more translucent though the bacon will still be supple and pliable. Remove with a heatproof slotted spoon, allowing excess fat to drain back into the pan before setting the bacon aside.
Reserve 2 tablespoons of the pan fat (leave it in the pan) and discard the remaining fat.
Add the onions to the pan and sauté over medium-high heat scraping all the browned bits from the bottom and sides of the pan. Sauté until the onions begin to turn translucent but are not limp. TIP: if you allow the onions to sit before stirring they will pick up more of the pan drippings.
Add the carrots, celery, parsley, herbes de Provence, beans and chicken stock; stir to combine.
Add the bacon to the pot; stir to combine.
Insert the chicken thighs and sausage into the stew so they are covered.
In a small bowl combine the bread crumbs and diced garlic. Sprinkle it evenly over the stew.
Bake for 1 hour and 15 minutes, periodically pressing the bread crumbs into the stew which will help thicken it.
Place the stew underneath the broiler to slightly brown the top crumbs and remove from oven.
Allow to sit for a few minutes, cut sausages into 2 inch pieces stirring them back into the stew, and serve. The stew is even more flavorful the second day too!