1. Heat the butter in a saucepan. Add the mushrooms and shallots and cook until limp.
2. Whisk in the flour and cook for 3 minutes.
3. Whisk in the broth, bring to just a boil, reduce the heat and simmer 20 minutes.
4. Heat a heavy skillet over a medium-high flame. Add a small amount of oil. Add the beef and cook to desired temperature. Serve topped with the warm sauce.