1 1/2 lb Beef tenderloin or sirloin cut in 2-by-1-in strips
1 c Beef stock
2 tb Flour
1 ts Dijon mustard
Directions
Step #1 SPREAD BEEF STRIPS on a baking sheet, Sprinkle top with salt & pepper, top this with onion slices & let this stand at about room temp for 2 hrs.
Step #2 Melt 2 tbsps butter in a skillet & stir in the flour.
Step #3 Mix in stock & heat, stirring until thickened.
Step #4 mix in mustard & remove from heat.
Step #5 In another skillet, melt remaining butter, add beef and onion & saute until browned.
Step #6 Add the beef (but not the onion) to the sauce & let simmer 15 mins.
Step #7 remove this from heat & stir in the sour cream.
Step #8 Serve onions separately or reserve for another use.