For the Pot Roast with Dumplings
1. Preheat oven to 325 F (160 C) and season all sides of roast with salt and pepper. Heat a Dutch oven or heavy-bottomed pot over medium-high heat and add oil, heating a minute more. Add roast and sear for 2 minutes on each side until browned. Remove roast and reduce heat to medium. Add onion, celery and carrots and stir until onions are translucent, about 5 minutes. Add garlic, thyme and bay leaves and stir one minute more.
2. Add back roast and pour in chicken or beef stock and diced tomato. Add stock or water if necessary, so that liquid comes halfway up roast (if liquid is higher, that is fine so long as roast is not completely submerged). Cover pot and bring liquid up to a simmer. Place pot in oven and cook for at least 3 hours, turning roast over after 1 1/2 hours.
For the Braised Vegetables
1. After 2 hours of cooking remove roast and cover. Strain liquid to remove first batch of vegetables (they will be mushy and will have already given their full flavour and nutritive value) and return to pot, skimming off excess fat.
2. Stir in potatoes, carrots, parsnips, turnips and dark beer and return roast to pot. Bring back up to a simmer then cover and continue cooking in oven until roast and vegetables both yield easily when prodded with a fork.
3. To serve, remove roast to a cutting board and cover with foil. Remove vegetables with a slotted spoon to a serving dish and toss with butter, salt and pepper and cover. If preparing dumplings (recipe below), place covered roast and vegetables back in oven (turned off) to keep warm while dumplings cook. Untie roast, slice and serve with vegetables, sauce and horseradish on the side.
For the Fluffy Dumplings
1. Sift dry ingredients. Add milk, oil and green onions or parsley and stir just until blended. After roast and vegetables have been removed from pot, drop spoonfuls of dumpling dough over braising liquid that is simmering. Cover pot and simmer for 10 to 12 minutes. Remove dumplings and serve.