Prepare Brown Sauce.
Meanwhile, in 12-inch skillet melt butter.
Add mushrooms and onion; cook and stir over medium heat till tender but not brown.
Push vegetables to one side of skillet.
Quickly brown meat, 1/3 at a time, in butter.
When all meat is browned, stir in Brown Sauce, dry sherry, salt, Worcestershire, and pepper.
Heat through, 5 to 10 minutes.