In a small saucepan bring cream, ginger, zest, and coriander seeds just to a boil. Remove pan from heat and let mixture stand, covered, 15 minutes.
In a bowl with an electric mixer beat yolks with sugar until mixture is thick and pale and forms a ribbon when beaters are lifted. Whisk yolk mixture into cream and heat mixture over moderately low heat, whisking, until a candy thermometer registers 160°F. Remove pan from heat and stir in vanilla. Strain sauce through a fine sieve into a bowl.
Serve sauce, warm or chilled, with fresh berries, poached fruit, or pound cake.
