|Dry mustard||1⁄2 Teaspoon|
|Sour cream||1⁄2 Pint|
Melt butter in pan, add finely chopped onion, saute gently until onion is tender.
Add sliced mushrooms, cook until mushrooms are well softened.
Add mustard, salt, pepper to taste, then stir in sour cream; heat together gently, simmer 5 minutes.
This sauce is equally good spooned over grilled (broiled) or pan-fried steaks, or over thick slices of roasted beef fillet.