Soubise sauce was originally a slow-cooked onion and Bechamel mixture used with various meats, game, poultry and vegetables dating back to the 1850s. Over the years, and through the hands of many chefs, it now has many variations. The simplest contains 3 ingredients, not counting salt and pepper. Most current chefs favor altering the sauce with beef stock along with the traditional Onion, Butter and Cream. The finished product is very creamy and rich when pureed.