Preheat oven to 400°F.
In a bowl, combine the sugar and cornstarch and mix well until all lumps disappear. Add the blueberries and lemon juice. Toss to combine.
Roll out half of the dough and fit it into a 9-inch pie pan. Fill with the blueberry mixture. Dot with the butter. Roll out the remaining dough. Moisten the edge of the bottom crust with water. Fit top crust over the filled pie. Trim and crimp edges. Make 2 or 3 vent holes in the top crust.
Brush the top crust with the cream or milk. Place the pie on a baking sheet with sides. Bake for 15 minutes. Reduce heat to 350°F and continue baking for 30 minutes or until the crust is golden and the filling is bubbling.