Heat oven to 350°. Layer potatoes in a 9-by-9-inch casserole dish. Combine cream, eggs, honey and cinnamon. Whip to blend well and season with salt and pepper. Pour over sweet potatoes. Bake for 1½ hours.
Cut the cold butter into small cubes and knead with the remaining ingredients to form a crumb topping. Sprinkle on top of sweet potatoes and return to oven until browned, 5–10 minutes