2 egg yolks
1/2 c. (1/4 lb.) butter, cut in sm. pieces, unsalted
2 tbsp. lemon juice

Over low heat in a small sauce pan, combine egg yolks, lemon juice and about 1/3 of the batter. DON'T HURRY! Let the butter melt slowly as you stir it occasionally. When melted, start adding the rest of the butter, a little at a time. Continue cooking and stirring until the sauce is smooth and slightly thickened. If sauce separates, remove from heat and whisk until smooth again. If it's still stubbornly non- associative, try adding a little cold water and whisk again.