Cut the pot roast into 3 equal-sized pieces and place them in a large bowl with the vegetables, garlic, bouquet garni, and red wine. Season with salt and pepper. Cover and marinate refrigerated for 24 hours. Preheat the oven to 250F. Drain the meat, reserving the vegetables and wine separately. In a large saucepan, boil the wine from the marinade, skimming occasionally. In an ovenproof casserole or Dutch oven heat 3 tablespoons of vegetable oil and brown the meat and vegetables. Pour the wine into the meat and vegetables. Add enough water to just cover the meat. Bring to a boil, cover, and place in the oven for 4 hours, stirring occasionally. Remove from the oven and let cool. Degrease the stew and strain the cooking liquid into a saucepan. Boil to reduce. To make the sauce, coarsely chop the shallots, parsley, and mushrooms and place them in a large saucepan with the wine and vinegar. Boil hard until the liquid is reduced to about 2 tablespoons. Add the cooking liquid from the beef and vegetables to the saucepan. Boil hard until reduced by half. Ten minutes before serving, cut the pot roast into slices and arrange them in a roasting pan. Pour the sauce over the beef and bake for 5 minutes at 425F. Serve with a celery purÄe.
