Caramelizing onions changes their flavour from sharp and pungent to sweet and complex. You cook them until they're deeply coloured and jam-like. The onion jam will keep for weeks when refrigerated. Use it to thicken soups and sauces, garnish grilled meats, poultry & seafood, fill omelets and sandwiches, stir into dips, toss with pasta... The prep time doesn't include the time to peel and chop the onions. This recipe was found in How to Cook Everything by Mark Bittman. This is a wonderful cookbook filled with simple tips and recipes for just about anything you can think of .