Preheat oven to 400° F.

Line a rimmed baking sheet with aluminum foil. Place blueberries on prepared baking sheet. Roast berries for 12 minutes, shaking the pan every 4 minutes for even cooking. Remove from the oven and allow to cool.

In a blender, puree blueberries and any accumulated juices until smooth. Set aside.

In a large bowl, whisk together egg yolks and sugar.

In a medium saucepan over medium heat, warm the milk and vanilla. When mixture is just starting to simmer (do not let it come to a boil), turn the heat down to low.

Slowly ladle the warm milk mixture into the yolks mixture, whisking continuously.

Pour mixture back into saucepan over medium heat. Stir with a heatproof rubber spatula or wooden spoon for 5 to 10 minutes, or until slightly thickened.

Remove saucepan from heat and whisk in crème fraîche until smooth. Then stir in the roasted blueberry puree. Allow to cool for 5 to 10 minutes, stirring periodically.

Transfer mixture to a bowl with a tight fitting lid and chill until very cold, preferably overnight, if chilling in the refrigerator. I speed up the process by chilling it in the freezer – I just set a timer to stir it well every 10 minutes, until it’s super cold.

Prepare ice cream according to the manufacturer's instructions. The ice cream will be a soft-serve consistency straight out of the machine. For a firmer ice cream, chill in freezer for at least a few hours or overnight.