Preheat oven to 350°.
Heat 1/3 cup of the Confit oil in a large Dutch Oven over medium heat.
Add onion, garlic, and black garlic and cook until tender.
Squeeze the garlic cloves from the confit from their skin and add to the oil. Add tomatoes, crushed in your hands.
Bring to a boil and cook, stirring occasionally until liquid has evaporated. Add beans and liquid.
Skim fat from the top of the confit and reserve. Pour 1/2 cup of the confit juice into the Dutch Oven. Bring to a simmer and season with salt and pepper.
Nestle chicken thighs into the bean mixture, skin-side up and the sausage and shallots from the confit.
Transfer to the oven and bake until the chicken skin is crispy and the cassoulet is nicely browned, about 2 hours.
Mix breadcrumbs with 1 Tablespoon of the confit oil and top the cassoulet. Cook until golden brown, about 20-25 minutes.
Garnish with fresh gooseberries, a sprig of thyme, and serve with toasted sourdough smeared with some of the confit fat.