Combine blueberries and sugar in a saucepan with a pinch of salt. Bring to a boil, mashing blueberries with a potato masher or fork. Simmer 5 minutes, stirring frequently, remove from heat and cool about 5 minutes. Pour the milk and blueberries into the blender and puree until smooth, then stir in the cream. Chill in a covered bowl a few hours or overnight. Freeze in an ice cream maker until firm and serve.