I have been pondering about the amount of butter it would take to coat your 100km square piece of toast and have come up with some frightening results. Somewhere between 10-15 grams of butter will cover a 10x10cm square piece of toast. Now we scale it up. Your 100x100km piece of bread would have the surface area of 10,000,000,000 (ten billion) standard pieces bread. So 15 grams x 10 billion = 150,000,000,000 grams divided by 1,000 (grams per kilo) = 150,000,000 kilos divided by 1,000 (kilos per ton) = 150,000 tons of butter to cover your piece of toast. Don't make me go into the troubles and implications of attempting to heat said piece of toast to a slightly burnt level...