Traditional sauce soubise is quite thick by today’s standards because it was often used to coat roasts (such as veal Orloff) or chops. A more contemporary version can be made by puréeing stewed onions with heavy cream and omitting the béchamel. This sauce can then be served as is or reduced to the desired consistency.
Peel and slice 5 pounds (2.25 kilograms) onions, and sweat them in 4 ounces (125 grams) butter. Be sure to use a heavy-bottomed pot and stir the onions almost constantly to prevent them from browning. The onion slices will shrink to about one-sixth of their original volume. When the onions are completely soft and there is no liquid left on the bottom of the pot, add ½ cup (125 milliliters) heavy cream. The sauce can be seasoned and served as is, or puréed in a blender or food processor or with an immersion blender, and strained. Be sure to purée it while it is still hot, or the cream will turn to butter. For a tangy sauce that is more appropriate for grilled foods, wine vinegar, red pepper purée, or tomato purée can be added to the onion sauce. The sauce can also be made more complex by adding reduced stock or roasting juices.