2 egg yolks
1 1/2 c. oil
1 tsp. dry mustard
1 tbsp. boiling water
2 tbsp. vinegar

Stir egg yolks and mustard in a flat wide dish. Add oil by DROPS, stirring constantly. When thick and creamy and all oil is incorporated, add vinegar. Finish with boiling water. If sauce should separate, use another egg yolk and stir in broken sauce DROP by DROP. This is a classic emulsion. Also gourmet mayonnaise. Does not keep forever.