Preparation Pour half and half into heavy medium saucepan. Scrape in seeds from vanilla bean; add bean. Bring to simmer. Whisk sugar, yolks and corn syrup in medium heatproof bowl to blend. Gradually whisk in hot half and half mixture. Return to saucepan. Stir over medium-low heat until custard thickens and leaves path on back of spoon when finger is drawn across, about 5 minutes (do not boil). Strain into bowl. Mix in crème fraîche and Calvados. Chill until cold. Transfer to ice cream maker; process according to manufacturer’s instructions. Transfer to covered container; freeze. (Can be made 3 days ahead.)
Preparation Pour half and half into heavy medium saucepan. Scrape in seeds from vanilla bean; add bean. Bring to simmer. Whisk sugar, yolks and corn syrup in medium heatproof bowl to blend. Gradually whisk in hot half and half mixture. Return to saucepan. Stir over medium-low heat until custard thickens and leaves path on back of spoon when finger is drawn across, about 5 minutes (do not boil). Strain into bowl. Mix in crème fraîche and Calvados. Chill until cold. Transfer to ice cream maker; process according to manufacturer’s instructions. Transfer to covered container; freeze. (Can be made 3 days ahead.)