Saute 8 to 12 whole or halved mushrooms in butter. Give them plenty of room in the frying pan so that they brown (don't crowd the mushrooms otherwise water is released and they boil).
Once the sauce is complete, stir in the mushrooms and serve immediately.
May be served over grilled, roasted or fried beef or potatoes. You can also saute your beef and use this mix as an excellent base for a meat sauce.