With a hot broiler, grill or frying pan, sear the briskets until they're well browned and crispy. Wash and cut the vegetables into a large, rough dice and place in the bottom of a large covered pan (squarehead). Add the beef, seasonings and stock. Cover and place in a preheated 375 to 400 degree oven and bake for about 6 hours. Check the meat with a meat fork. The briskets should be extremely fork tender (practically falling apart). When done lift from the stock with a fork and a spatula underneath to a holding pan to cool slightly.
Meanwhile -- into a large plastic food bucket, strain the vegetables and stock through a medium hole china cap (sieve). Using a mallet or ladle squeeze some of the vegetable pulp through into the stock for flavor and texture. Discard the squeezed veggies. Cool the stock so the fat will rise to the top.
While the meat is still warm cut out the large pieces of meat separating it from the fat layer in the middle. Scrape off any excess soft fat and discard it. Keep the meat pieces (pot roast) to eat soon or refrigerate them.
To Make Gravy: Heat the Pot Roast Stock separately. In a large heavy saucepan heat the beef fat, boiling out any water particles (takes a couple minutes). Make a roux by whisking in the flour and cornstarch stirring constantly -- cooking a few minutes. Continue stirring (it could burn) browning slightly is okay. It adds color to the gravy. Add some of the hot stock gradually. Stir swiftly to break up lumps and make a smooth paste. Add more stock to thin to the desired consistency. Let simmer 20 to 25 minutes, stirring occasionally. Check for color, taste and thickness. Adjust color if desired with a few drops of Gravy Master or Kitchen Bouquet. Add salt and pepper and more stock if needed.
Garnish: Simmer carrots, celery and onion in a little stock to soften slightly. Cool until needed. Dip in stock to reheat and arrange on top of gravy on the meat.
Slowly reheat Pot Roast in hot stock. Remove from stock to a cutting board. Slice the meat thinly on the bias against the grain of the meat. Arrange on the plate, ladle on the gravy and garnish with the julienne vegetables, if desired. Serve with fresh mashed potatoes and a vegetable. This is a meal to enjoy.
** Bruce recommends Black Angus Briskets because of the higher meat yield and quality. Also Briskets are fatty with excellent flavor so when they're well done the fat cooks out and they stay moist and tender.