Preheat the oven to 375°F.
Season the chicken with 1 teaspoon of the salt and ½ teaspoon of the pepper.
In a large skillet over medium-high heat, add 2 tablespoons of the oil.
Add the chicken thighs to the hot oil and cook, undisturbed, until the edges turn opaque and the bottoms are browned, about 6 minutes. Make sure to adjust the heat as needed to prevent scorching. Step 5
Flip the chicken and cook until it reaches an internal temperature of 165°F, about 4-5 minutes. Transfer the chicken thighs to a plate and do not clean the pan.
Place the skillet with the chicken drippings over medium heat.
Add 1 tablespoon of oil, the onion, and the sausage. Cook while stirring often until the onion is tender and lightly golden, about 6 minutes.
Add the garlic, 1 tablespoon of the thyme, the allspice, the remaining salt, and the remaining pepper and cook, while stirring often, until fragrant, about 2 minutes.
Add the wine and tomato paste, stirring to combine.
Bring the sausage mixture to a simmer.
Cook, stirring often, until the flavors have melded together and the wine has reduced slightly, about 1-2 minutes.
Add the beans, chicken stock, and 2 tablespoons of the oil, and cook, stirring to combine, until the sausage mixture comes to a simmer.
Shred the chicken into bite-size pieces.
Add the chicken and any accumulated juices on the plate to the sausage mixture.
Transfer the cassoulet mixture to an 8x11-inch baking dish, spreading it out evenly into a layer.
In a large bowl, add the breadcrumbs and the remaining oil and toss to combine.
Sprinkle the breadcrumbs over the cassoulet mixture in the baking dish.
Bake until the dish is heated through, the top is browned, and the sides are bubbly, about 20 minutes.
Serve garnished with the extra thyme sprigs.