How to Make It
Drain and rinse the beans. In a large saucepan, cover the beans with the stock; bring to a boil. Cover and simmer over moderately high heat until the bean skins begin to split, 20 minutes.
Preheat the oven to 350°. Heat the olive oil in a large enameled cast-iron casserole. Add the onions and garlic, cover and cook over low heat until the onions soften, 5 minutes. Uncover and cook over moderate heat, stirring, until the onions are browned, 4 minutes. Add the tomatoes, maple syrup, vinegar, parsley, sage, bay leaf and 3/4 teaspoon of salt; bring to a boil. Add the beans and their cooking liquid and bring to a boil..
Cover and bake for about 4 hours, stirring occasionally, until the beans are very tender and the sauce is thick. Remove the bay leaf, season the beans with salt and pepper and serve.