Onions should have the stem and root ends removed. Onions should be left whole.

Place the onions, butter and broth in a slow cooker set on low and cook until the onions are deep golden brown and very soft, 12 to 24 hours. Different slow cookers will take different amounts of time. It's almost impossible to overcook this, so go fot he deepest brown.

Use the onions and liquid to flavor soup, stock and stews. They make wonderful additions to risotto, a perfect pasta sauce, and the world's best pizza topping (first drain off the liquid).

Store in zippered plastic bags in the refrigerator up to 2 weeks, or in the freezer up to a year.