Easy and Elegant Beef Stroganoff

Yield:	6 Servings
Categories:	Main Dishes

1	lb	Beef sirloin steak, cut
		Across grain - bite size
1/2	ts	Ground pepper, prefer. white
2	tb	Butter or margarine
6	oz	Portobello or white mushroom
6		Scallions, sliced
1	cn	Beef gravy (10 1/2 oz.)
2	tb	Balsalmic vinegar or 1 Tbs.
		Red-wine vinegar
1/3	c	Light sour cream