In a medium saucepan, combine the frozen blueberries, powdered sugar, cornstarch, and lemon juice. Cook over medium heat for 3-5 minutes, stirring constantly until juicy but not bursting.

While the blueberries are cooking, preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

On a floured surface, roll out the thawed puff pastry to about 10 inches by 15 inches and cut it into six 5-inch squares.

Place a spoonful of the blueberry mixture in the center of each square.

Fold the pastry over the filling to make a triangle. Seal the edges and make three small slits on top to allow steam to escape.

Brush each turnover with melted butter and sprinkle raw sugar on top. Bake for about 20 minutes or until golden brown.

Combine the remaining powdered sugar and milk in a bowl to make a simple icing. Drizzle over completely cooled turnovers.