Myzithra is a salty sheep's milk cheese; I can find it in any grocery store that has a good "upscale" deli section here. Is there a Trader Joe's in Toronto? They'd have it, if so. (It's been a year or so since I had an assignment out there; I forget the grocery stores in the downtown area...)

It comes in two varieties, a soft cheese like Ricotta or Chevre, and a firm version like parmesan or romano. What I use is the firmer version. It has a milder flavor than most Italian "grating" cheeses; I'd try a blend of about two parts grated Asiago to one part Romano, the mildest variety you can find.

A good strong Italian sausage fry goes wonderfully with this dish, by the way. Last time I made this I had some chicken-basil sausage that was really tasty!