In a large uncovered pot or Dutch oven, sear the beef in cooking oil for about 5 minutes.
Add 1 cup of water, beef cubes, salt & pepper, then bring to a boil. Then reduce the heat. Cover and simmer for 1 1/2 hours until the beef is very tender.
Then add potato, carrot, turnip, onion, and mushroom. Stir and cover. Simmer for 20 minutes or until the vegetables are tender.
Once the vegetables are tender, stir 2 tablespoons of flour into 1/4 cup of water, and mix until smooth. Gradually, stir the flour mixture into the simmering liquid. Stir until thickened.
Last, add sour cream to the mixture. Stir until heated through. Do not let it boil. Turn the heat off and garnish with scallions.