Beat together yolks and remaining ¼ cup sugar in a medium bowl with an electric mixer until thick and pale, about 1 minute. Add milk mixture in a stream, beating until combined well. Pour mixture into reserved saucepan and cook over moderate heat, stirring constantly with a wooden spoon, until mixture coats back of spoon and registers 175°F on thermometer (do not let boil). Immediately remove from heat and pour through a fine-mesh sieve into a metal bowl. Set bowl in a larger bowl of ice water, add cream and stir until cold, 10 to 15 minutes.