In a small saucepan with a splash of water, heat the blueberries over medium-low heat, stirring frequently. They will begin to turn a deeper blue and release liquid. Continue stirring and cooking under the blueberries are very soft or a complete puree, depending on how much texture you like. You can also puree them completely after they have cooled.
Heat the heavy cream and vanilla extract on medium heat in a medium saucepan. While the cream is heating, whisk the egg yolks and sugar together. Once the cream is simmering, slowly pour it into the egg yolks and sugar while whisking.
Pour the mixture back into the saucepan and turn the heat down to medium low. Stir in a figure 8 motion for several minutes until the ice cream base is thick enough to coat the back of a wooden spoon. Remove from the heat and stir in the buttermilk. If using, whisk the powdered buttermilk into a small amount of the liquid and then incorporate it into the ice cream base.
Stir in the cooked blueberries.
Allow to chill completely in the refrigerator.
Prepare in an ice cream machine according to manufacturer's instructions.