Place the brisket, fat side up, in a roasting pan slightly larger than the cut of meat with at least 2″ sides. Sprinkle the onion soup mix, organic seasoned salt, and Chinese five spice over the brisket. Distribute quartered onion, garlic cloves, and halved prunes around the beef in the pan. Mix together the remaining liquid ingredients and enough dry red wine to cover halfway up the sides of beef. There is no need to brown the beef beforehand.
Cover with parchment paper and secure with foil on top. (Foil should not touch top of meat.) Bake for 4-5 hours. Check after about two hours to make sure that the liquid has not evaporated. Add wine if needed. Test for tenderness after 4 hours. In the last half hour of cooking remove the parchment paper and foil to allow a crust to form. Remove from oven when the brisket is fork tender. There will be some liquid left in pan.
Refrigerate in pan before slicing thinly across the grain. To reheat, place sliced beef in crock pot, deglaze the pan with beef broth, and pour over sliced beef. Add enough broth to cover. Beef will hold in the crock pot for a few hours. Great for a buffet. The slices will be great for sandwiches or over mashed/baked potatoes.