In a small bowl, break up the egg yolks with a fork. Add about a ladle of the hot mixture to the yolks, whisking constantly, to temper the eggs. Pour back into the pan with the remaining hot mixture. Return to the heat and bring to a boil, stirring constantly. Remove from the heat and add the butter, zest and citrus juices. Stir until smooth. Set aside.
MERINGUE
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