Boil potatoes in salted water with skin on until tender; cool slightly (just until you can handle them), peel and cool completely. Grate potatoes coarse. Butter a casserole dish and mix potatoes with sour cream, cheese, salt, pepper, milk, and chives. Sprinkle breadcrumbs over top of potatoes, drizzle with butter and (at this point you can refrigerate up to a day) bake 1 hour at 350.