Heat milk, cream and vanilla in double boiler over simmering water until hot but not boiling.
Whisk egg yolks and sugar in a bowl. Stir a small amount of the hot milk mixture into egg yolks; stir the egg yolks into the hot milk mixture gradually. Cook for 10 minutes or until sauce coats back of spoon. Do not allow to boil or the sauce will curdle. Remove from heat and then stir in liqueur.
The sauce will continue to thicken as it cools. Cut strawberries into halves or slices. Spoon strawberries evenly into four wine goblets, martini glasses or dessert bowls. Drizzle sauce over strawberries. The sauce may be served warm or chilled. Serves 4