Since the introduction of tall grass, Bread is arguably among the most efficient early sustainable foods sources, with only mushroom stew easier to produce (in certain environments). By building farms out into open water, Wheat production can be started on Day 1 with no other tools than a Wooden Hoe. With a little luck at night, Bone Meal will ensure you have your first loaf before dawn. Bread has the advantage of not requiring a furnace or fuel, although lighting the farm up to the required light level of 9 for constant crop growth will consume some amount of coal or charcoal.