The onion is one of my favorite vegetables. It is known for its versatility in many dishes and serves as the base for many soups and stews. Select onions that are very hard with a paper-like skin.
The goal when sweating an onion is to begin to break down the bitter tasting compounds into sugars. However, the sugars are not allowed to break down into their carbon compounds. Place chopped onions in a Dutch oven or in a large pot on medium to low heat and cook, covered, for about 20 minutes -- or bake the onions in a 350° oven for about 30 minutes. Keeping the pot covered will prevent the nutrients and flavors of the onion from escaping during the cooking time. Take care that the onions do not burn. You can store the onions periodically to reduce the risk of burning.
When the onions are done, they will be translucent and glossy but not golden brown. If the onions appear to be browning, stop cooking; you have reached the sweating the point.
Caramelizing takes the onions a step sweeter beyond sweating. The sugars begin to break down into carbon compounds. However, by performing this process slowly, we create very complex compounds instead which result in a very deep, layered flavor. Be warned, in order to achieve a very deep caramelization, the process will take several hours. The trick is to allow the onions to repeatedly form caramel compounds and dissolve those compounds in a liquid, redispersing them throughout the onions before they have a chance to burn.
Begin by completely filling a Dutch oven or oven safe pot with sliced or chopped onions. Bake at 400°for 1 hour. Deglaze the pan with brandy or cognac, scraping any browned bits (known as fond) off the sides and bottom of the pan with a wooden spoon. Scrape off the spoon to return any remaining fond into the pan. Mix well.
Reduce the temperature to 350° (you don't have to wait for the oven to cool down) and bake for another hour. Deglaze again, then move the Dutch oven to the stove top. Turn heat to medium, and cook uncovered until the liquid evaporates and another layer of fond forms on the bottom of the pan, about 10-20 minutes.
Deglaze the pan a third time, this time with white wine. Allow the liquid to evaporate again, and another layer of fond to form, and deglaze the pan one final time with an equal amount of red wine. Allow the liquid to evaporate one final time; stir well and remove from heat.
You can turn these caramelized onions into a fantastic onion soup by adding a sprig of thyme, equal parts chicken and beef stock (and some veal stock, too, if you have it) until the onions are covered. Add salt and pepper to taste, and simmer for about 30 more minutes. Serve with toasted crusty bread and cheese.