1. On Day 1 cover beans with cold water and let stand 24 hours.
2. On Day 2 drain beans. Place in a medium saucepan, add bay leaf, thyme, 1/2 teaspoon of the salt, and water to cover. Over high heat bring to a boil, reduce heat to maintain a simmer, and cook until tender (about 1 hour). Drain beans, reserving 1 cup liquid. Transfer beans to a bowl, add reserved liquid, cover, and refrigerate.
3. On Day 3 in a large skillet over moderate heat, melt butter. Add onion, carrot, and celery and saute 3 minutes. Add sage and cook 1 minute. Stir in beans with their liquid and simmer 5 minutes. Remove from heat, cool, cover, and refrigerate 2 days.
4. On Day 5 preheat oven to 400 degrees F. Butter an 11by 13-inch baking dish. Season beans with salt and pepper, then transfer to baking dish. Drizzle cream over dish and dot with bread crumbs. Bake until hot and lightly browned (15 to 20 minutes). Serve from the baking dish, if desired.