How to Make It
Heat the olive oil in a large enameled cast-iron casserole. In 2 batches, cook the pork belly over moderate heat, stirring occasionally, until lightly browned on all sides, about 10 minutes. Transfer the pork belly to a plate. Add the onion to the casserole and cook over moderate heat, stirring, until softened, about 5 minutes. Add the pork belly and the beans, tomatoes, thyme and bay leaves. Add the Ham Hock Stock and bring to a boil. Cover partially and simmer over low heat until the beans are almost tender, about 45 minutes. Skim off the fat with a ladle.
Add the quince to the beans and season with salt and pepper. Cover partially and cook until the pork, beans and quince are very tender, about 45 minutes longer.
Preheat the oven to 425°. Transfer the beans to one 3-quart or two 1 1/2-quart baking dishes and bake until the top is lightly browned, about 30 minutes. Sprinkle with the chives and serve.