Bearnaise Sauce - cooking recipe

Ingredients

2 Tbsp. red wine vinegar
1 1/2 tsp. chopped green onion
1 1/2 tsp. tarragon
1/8 tsp. cracked black pepper
4 egg yolks
3/4 c. butter or margarine
1 Tbsp. chopped parsley

Preparation

In top of double boiler, combine first 4 ingredients.
Over high heat, heat to boiling; boil until vinegar is reduced to 1 tablespoon.
Place double boiler top over double boiler bottom containing hot, not boiling water.
Add egg yolks; cook, beating constantly with wire whisk, until slightly thickened.
Add butter, 2 tablespoons at a time, beating constantly with whisk until butter is melted and mixture thickened.
Stir in parsley.
Serve with tenderloin.