Heat oven to 400°F. Mix breadcrumbs and butter together in small baking dish. Bake, tossing occasionally, until light golden brown and crisp, 8 to 12 minutes. Cool to room temperature; set aside.

Bring beans, whole garlic cloves, onion halves, ham hock, salt, pepper, and 8 cups water to a boil in stockpot over high heat. Cover, reduce heat, and simmer until beans are almost fully tender, 20 to 30 minutes. Do not overcook the beans. Drain beans and discard garlic, onion, and ham hock.

Brown bacon in large Dutch oven over medium heat until fat is well rendered. Remove bacon with slotted spoon and drain. Carefully remove all but about 2 tablespoons of bacon grease from pan.

Place Dutch oven over medium-high heat. Season pork loin cubes with salt and pepper. Working in 2 batches, sauté half the pork until well browned, about 5 minutes. Set aside on plate. Repeat with remaining pork; set aside.

Add chopped onion to Dutch oven and cook, stirring occasionally, until softened, 3 to 4 minutes. Add 3 cloves minced garlic, tomatoes, tomato paste, thyme, and bay leaf to onions; cook until fragrant, about 1 minute.

Add wine and simmer for 5 minutes. Stir in chicken stock; increase heat to high and bring to a boil. Cover pan; reduce heat and simmer 40 minutes. Remove cover and simmer for 30 minutes. Remove thyme sprigs and bay leaf.

Gently stir in browned pork cubes, andouille sausage, drained beans, and reserved bacon. Season with salt and pepper, if desired.

Heat oven to 425°F. Sprinkle panko topping evenly over surface of cassoulet. Bake for about 15 minutes until meat is hot and breadcrumbs are deep golden brown. Poke a small hole in the panko crust and let stand 10 minutes before serving.