Some of my favorite dishes call for ricotta cheese, be it anything from a lasagna to cannoli. Arguably this is a very easy thing to find in the States (and presumably elsewhere), so I'd never thought about it. But, living in Japan, I have yet to find it anywhere - supermarkets, import shops, or cheese shops. (Mind you, cheese is a pretty rare thing here, and a delicacy at that.)

So, being unable to buy it anywhere, what are my options? Is there a substitution I can try or is it something I can make at home?