If it coats a spoon nicely, that is enough. Add the remainder of the sherry to the sauce, and strain it again into clean containers that have been rinsed with boiling water. Cover with Saran wrap, and cool. If any fat rises to the top of the sauce, leave it until you are ready to use it, as it protects the sauce from airborne spores. This is the basic brown sauce, and extra stock has been added, so that it is made as Espagnole and finishes as Demi-Glace.
Optional ingredients are just for flavor, and to get an extra meal out of the work.
After all, the chef deserves a nice lunch. If you want to freeze it, omit the cornstarch and wine slurry, and bind it after you thaw the frozen product, as it will hold up better that way. All rights reserved. Inc. All rights reserved.