Heat oil in a large pot over medium-high heat. Add beef, onion, and 1 tsp steak seasoning. Stir well and sprinkle with the remaining 1 tsp steak seasoning. Cook until beef is browned (about 10 mins).
Pour in 2 cups water, enough to cover the ingredients. Bring to a boil, scrape the bottom of the pan, then reduce heat, and let it simmer for 2 hours until the beef is tender.
Remove beef and celery pieces from the pot; discard celery. In a bowl, whisk gravy mix with 4 cups water. Add the gravy mixture back into the pot, bring to a boil, and stir beef in.
Add carrots, turnip, and potatoes. Cover and simmer for 20 mins (for carrots and turnip) and an additional 20 mins (for potatoes).
For the dumplings: Mix flour, baking powder, and salt. Cut in shortening with a pastry cutter or two knives until crumbly. Stir in milk to form a dough.
Drop heaping tablespoons of dumpling dough onto the stew in the pot. Cover and simmer for 20 mins (do not peek).
Reserve 2 cups of gravy, then pour the rest back over the dumplings. Stir lightly and serve.
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