1. In the top of a double boiler, beat egg yolks to blend with maple syrup.
2. Nest in pan over simmering water and stir until mixture is thick enough to coat a metal spoon, about 10 minutes.
3. Immediately nest pan in ice water and stir mixture until cold, about 12 minutes.
4. Meanwhile, in a deep bowl with a mixer on high speed, whip cream until it holds soft peaks. Fold into maple mixture.
5. Pour into an ice cream maker (l 1/2-qt. or larger capacity). Freeze as directed until mixture is firm enough to scoop, dasher is hard to turn, or machine stops.