Combine ¼ cup sugar, blueberries and fresh lemon juice in a small, non-reactive saucepan set over medium heat. Bring to a boil and mash berries. Puree blueberry mixture and strain through a fine mesh sieve. Set aside.
Combine milk, 1 cup heavy cream, remaining sugar, salt, and ½ vanilla bean** in a medium saucepan set over medium heat. Stir to dissolve sugar.
Whisk egg yolks in a small bowl.
When milk mixture begins to steam, temper the eggs yolks by slowly drizzling 1 cup of the warm liquid into the yolks while continuously whisking. Pour egg mixture into saucepan followed by the blueberry puree. Stir to combine and continue cooking until mixture coats the back of a wooden spoon or rubber spatula. (175° F on an instant read thermometer)
Pour batter through mesh strainer into remaining 1 cup heavy cream. Stir and cool to room temperature over an ice bath. Cover and chill thoroughly, 4-6 hours or overnight.
Churn according to manufacturer's directions. Transfer churned ice cream to a freezer safe container. Cover and freeze until solid.