In a medium metal bowl sprinkle gelatin over cold water to soften 1 minute. Whisk in yolks and sugar and set bowl over a saucepan of simmering water. Cook egg mixture, whisking constantly, until an instant-read thermometer inserted 2 inches into mixture registers 160°F. (Tilt bowl to facilitate measuring temperature.) Remove bowl from pan and with an electric mixer beat egg mixture until cool and thickened, about 5 minutes (mixture will be very sticky). Beat in pumpkin and spices. Chill pumpkin mixture, covered, until thickened and cool but not set, about 1 hour.