Bring milk and vanilla seeds and pod to a simmer in a medium saucepan over medium heat. Discard vanilla pod.
Beat egg yolks and 1/2 cup sugar in a medium bowl. Slowly pour 1/4 cup hot-milk mixture into yolk mixture, whisking to combine. Add remaining milk mixture, 1/2 cup at a time, whisking well after each.
Prepare an ice-water bath. Return yolk mixture to pan, and cook over low heat, stirring often, until mixture thickens and coats the back of a spoon, 3 to 5 minutes.
Remove pan from heat, and stir in cold cream. Pour custard through a fine sieve into a medium bowl. Set the bowl in the ice-water bath, and let stand, stirring occasionally, until cold.
Meanwhile, toss peaches with remaining 1/4 cup plus 2 tablespoons sugar, and let stand to release juices, about 30 minutes. Mash peaches until a coarse puree forms. Mix peaches into custard.
Freeze in an ice cream machine following the manufacturer's instructions.