In a large cast iron pan or dutch oven (or other ovenstove proof pan), Cook and stir beef and onion in oil till browned. Stir in hot water, salt and pepper, tomatoes, paste, and cleaned sliced mushrooms. Do not clean mushrooms in water, use a mushroom brush or damp paper towel. Heat to boiling stirring occasionaly and cook for about 1 1/2 hours till beef is tender.Add carrots and celery and cook another 30 minutes. Mix water and flour and blend well. Whisk into meat mixture stirring constantly till thickened. Reduce heat and make dumplings. For dumplings, mix all ingredients till a soft dough forms. Beat vigorously 20 strokes. Drop dough by spoonfulls onto hot meat mixture and bake in preheated 450 oven for 10 minutes or till dumplings are browned on top.