Combine first 3 ingredients in a medium bowl.
Process peach mixture, in batches, in a food processor until smooth, stopping to scrape down sides. Set aside.
Whisk together yolks and milk in a heavy saucepan over medium heat; cook, stirring constantly, 20 minutes or until mixture thickens and coats a spoon. Do not boil.
Remove from heat; whisk in peach mixture, half-and-half, lemon juice, and ground cinnamon. Cover and chill 4 hours.
Pour mixture into freezer container of a 6-quart electric ice-cream maker. Freeze according to manufacturer's instructions. (Instructions and times will vary.) Garnish, if desired.
Note: For testing purposes only, we used a White Mountain 6-Quart Electric Ice Cream Freezer.