BOWL:

2 c. water
1 lg. onion
Salt
Lemon juice
12 fresh thin-sliced mushrooms
1 or 2 lb. filet or sirloin of beef

JAR:

1/2 c. red wine vinegar
2 tsp. Dijon mustard
1/2 tsp. salt
Dash pepper
1/2 tsp. chervil or parsley
1 c. salad oil

Roast rare and slice beef thin. Bring water to a boil. Add salt, lemon juice, and 1 large onion, sliced into rings. Remove immediately and drain. Place in a bowl. To the bowl add the mushrooms and beef.

Combine all the jar ingredients and shake well. Pour over meat and mushrooms. Cover with plastic wrap and chill overnight, basting once or twice. Remove from oil and serve on lettuce-lined platter. Serves 4 or 5.