• Whisk the egg yolks with 20 ml lukewarm water at the top of a double-boiler. Place over simmering water in the bottom half of the double-boiler.
• Add the butter bit by bit, beating all the time. Do not allow to boil.
• Add the boiling water gradually, still beating.
• Season with salt, pepper, and lemon juice, continue beating and use at once.

Variations

• Mousseline: Fold 50 ml whipped cream into the finished sauce and serve with grilled salmon, asparagus, artichoke hearts, broccoli, or lamb cutlets.
• Maltaise: Use the juice and finely grated rind of a Seville orange instead of the lemon juice and serve with fried scampi, soles, broccoli, or asparagus.
• Divine: reduce 25 ml sherry and 25 ml whipped cream to 12,5 ml liquid over high heat and stir into the finished sauce. Serve with chicken or sole.

Note

• Beat egg yolks for at least 3 minutes as they must thicken before you continue with the sauce.
• Eggs must be at room temperature.
• It is important to beat the eggs and the butter slowly so that they will form an emulsion.
• Use only the best ingredients available. Although the purists prescribe unsalted butter, ordinary butter will do. Margarine should not be used.