4 egg yolks 1/2 cup butter, room temperature 2-3 Tbsp lemon juice salt white pepper
Cook egg yolks and 1/3 of the butter in the top of a double boiler, stirring rapidly over boiling water until butter melts. Add 1/3 more of the butter, stirring rapidly. Continue process until all of the butter is melted; the mixture will thicken. Stir constantly.
Remove pan from water, stir in lemon juice, 1 tsp at a time. Stir in a dash of salt and pepper. Heat again over boiling water, stirring constantly until thickened. Remove from heat. If sauce curdles, beat in 1-2 Tbsp boiling water.