Mince the lemon balm and marjoram leaves, or chop finely. Place in the top of a double boiler with all the other ingredients except the egg yolks. Mix well together, let stand for two hours, uncovered. Over hot water, beat in the egg yolks with a wire whisk. Cook, stirring constantly, for five mins until thick and creamy. Spoon into sterilized jars, cool. Cover tightly, store in the refrigerator for up to one month.
