Custard Dressing - cooking recipe

Ingredients

1 egg + 1 yolk, lightly beaten
1/2 c. sugar
1 1/2 tsp. cornstarch
1 tsp. dry mustard
1/4 c. vinegar
1/4 c. water
3 Tbsp. soft butter
1/2 c. mayonnaise

Preparation

Whisk eggs, sugar, cornstarch and mustard together.
Slowly whisk in water and vinegar.
Cook until mixture thickens.
Remove from heat and stir in butter and then mayonnaise.
Chill.