Set up your water bath and heat to 82.2ºC/180ºF. Cover the the container to help speed up heating and retain the heat.
Shuck, wash and remove the corn kernels. Place in a medium saucepan along with the cream, milk, sugar and salt. Bring to a simmer. Allow to cool and infuse. For a more pronounced corn flavour, combine the heated mixture in a blender, then strain. Or the strain the liquids into a blender or bowl. Save the kernels for another dish!
With your warm liquids in a blender or bowl, add the egg yolks and vanilla (if using), and blend to combine. Spoon off the foam.
Pour into a bag suitable for sous vide and use the displacement method to remove as much air as possible, while submerging in the heated water. Cover and cook for 30 minutes.
Close to the end of the cook, prepare an ice bath (cold water and ice). When the custard is ready, remove it from the water bath and immediately place it in the ice bath. Allow to cool completely.
Once cooled, whisk in the creme fraiche and place in the refrigerator for a couple hours to chill, then churn it according to your ice cream maker manufacturer's instructions. Fold in your fruits and zest.
Transfer to a freezer-safe, airtight container and freeze overnight for best results. Enjoy!