In a saucier, or a pan that has sloped sides, stir together the whole milk, heavy cream, kaffir lime leaves, lime zest lime, and the vanilla pod and scraped beans.
Heat the contents of the pot on low, for 5-7 minutes, or until the milks begin to steam. Turn the heat off and allow the kaffir lime leaves to steep in the hot milk for 10 minutes.
While the leaves are steeping, whisk together the egg yolks, granulated sugar, and salt in a mixing bowl.
Temper the eggs by whisking a cup of the hot milk into the eggs in a slow stream. Once all of milk has been whisked in, slowly pour the eggs into the pot of milk in the same way- a slow stream- whisking constantly.
Cook the mixture over medium-low heat until thickened (about 6-8 minutes), stirring constantly. When properly thickened, the custard should coat the back of spoon, as well as hold a line drawn through it with your finger.
Once the custard has thickened, transfer it to a mixing bowl**. Place the bowl into a larger bowl filled with ice and chill the custard base until ice cold. Now, cover and place the bowl into the refrigerator for 8-24 hours and allow the custard to age.
After chilling, pour the custard through a strainer to remove the kaffir lime leaves and vanilla bean.
Churn the custard to a soft serve consistency in your ice cream maker following the machine's manufacturer's guidelines for churning times. While your custard is churning, place a stainless steel bowl into the freezer for later use.
After the custard has finished churning, pour the custard into the frozen stainless steel bowl. Gently fold the chopped blueberries into the custard, then pour the custard into two quart-sized ice cream containers.
Cover and freeze the custard for 4-6 hours, or overnight. After your frozen custard has had a chance to firm up, allow it to warm on the counter for 15 minutes before scooping and enjoying.
Notes
**At this point, you can strain the leaves and vanilla bean from the custard, or for a stronger flavor, chill the custard with the leaves and vanilla in it.This frozen custard can be kept, frozen, for up to 2 months.