According to Gamp's Law of Elemental Transfiguration:
Your mother can’t produce food out of thin air, no one can. Food is the first of the five Principal Exceptions to Gamp’s Law of Elemental Transfigura—... It’s impossible to make good food out of nothing! You can Summon it if you know where it is, you can transform it, you can increase the quantity if you’ve already got some...
So by using Aguamenti to create water, then transfiguring said water into, say, a hamburger, would one potentially have infinite food. (This is saying water classifies as food. To this end, what decides what classifies as food or not to magic itself?)
