Slice steak into thin strips about 8 cm long. Brown in oil in bottom of pressure cooker. Add onions, bell pepper and paprika; cook, but don't brown. Add garlic (Mom used a spoonful of garlic ground in oil). Add stewed tomatoes and spices. If not tomato doesn't seem strong enough, add small can of tomato paste or sauce. (Don't add if can avoid it.) Add blended celery at this point, plus mushroom pieces. (Liquid would make it unnecessary to add tomato paste, she says.) Add 8 oz box of macaroni and push beneath liquid, making sure all is covered. Put on cover and add weight of 15 pounds, over high heat. After starts popping, cook 4-5 minutes, but no longer. Let pressure off, remove lid and stir in cheese. Serve.