Pull the dried beef apart, tearing into small pieces.
If beef is very salty, rinse first in warm water, then drain well. Melt butter over low heat in a medium saucepan; add onion and cook until tender. Add beef and cook gently until edges curl. Blend in the soup, water, evaporated milk, and Worcestershire sauce. Heat through, but do not boil. Serve over buttered toast or baked potatoes.
Serves 4.