I always buy the largest yellow onions I can find, aka lazy cook's onions. You get more onion to peel ratio with a large onion than small ones. And you work less, too. Quantity... 3 or 4 pounds onions should do nicely. As a rule of thumb, when the food processor's container is a bit over half full of chopped onions, I call it OK. You'll need 2 tablespoons brown sugar and please use freshly ground black pepper. You're worth it.
You need to stir often while you are caramelizing the onions, specially when the water is all but gone. I have a straight edge wooden spoon to scrape the bottom of the pot well at that stage. It will stick slightly, but you need that fond to bring that added flavor dimension to your onion soup. If it doesn't stick a bit, you may as well open a can of condensed onion soup and save yourself a bit of trouble. When the soup is all done simmering, you won't need to scrub the pot. I guarontee. A bonus: it freezes well, too.
Sylvain.
