Whisk the egg yolks in a mixing bowl -- preferably one with a spout if you have one. Whisk in the egg, then whisk in the maple syrup.
Set a sieve or mesh colander over a second mixing bowl and set aside.
In a heavy bottomed saucepan, combine the cream and milk. Heat over medium until mixture just starts to simmer around the edges. Carefully whisk about 1 ½ cups of the hot milk mixture into the egg mixture, then pour the egg mixture into the saucepan, whisking constantly.
Whisk until mixture thickens somewhat and hits 175 degrees F. (Note: I use a deep fry thermometer for this).
Remove from heat and pour the hot custard through the sieve or strainer into the bowl. Add vanilla. Let cool for about 25 minutes at room temperature, then transfer to the refrigerator and chill for 6 hours or until thick and cold.
Freeze mixture in an ice cream maker using the manufacturer's directions.