Roll out the dough on a lightly floured surface to a thickness of about 1/8-inch thick. Carefully fit the dough into a deep 9 1/2 or 10-inch pie dish and trim the edges, leaving a 3/4-inch overhang. Fold under the edge of the dough and press along the rim of the pie pan to form a high, fluted border. Refrigerate the pie shell for at least 30 minutes.
Preheat the oven to 400 degrees F and position a rack in the center of the oven.
Line the pastry with lightly buttered parchment paper or aluminum foil (buttered side down) and fill with pie weights or dried beans. Bake until the crust is just set, about 12 minutes. Remove the paper and weights and bake until the crust is just golden, 8 to 10 minutes. Remove from the oven and brush the pastry with the egg white. Transfer to a wire rack to cool. Reduce the oven temperature to 375 degrees F.
In a heavy saucepan combine the milk and cream and heat until mixture just comes to a simmer. Whisk the eggs, 3/4 cup of the sugar, salt, nutmeg, and vanilla together to combine. Add the hot milk mixture to the egg-sugar mixture and whisk to blend.
Transfer custard mixture to the pie shell and bake until the custard is set but still slightly wobbly in the center, 40 to 45 minutes. Transfer to a wire rack to cool. When cooled, transfer to the refrigerator to chill.
While the pie is baking, make the blueberry topping. Combine the blueberries and cold water in a heavy, nonreactive saucepan. Bring to a boil. In a small bowl, stir together the remaining 1/2 cup sugar, cornstarch, lemon juice and lemon zest. Stir the sugar-cornstarch mixture into the boiling blueberries and stir well to combine. Cook until thickened, stirring constantly, about 5 minutes. Remove from the heat and transfer to a small bowl. Place a piece of waxed paper or plastic wrap directly onto the surface and chill, stirring occasionally, until completely cooled, about 2 hours.
When both the pie and the blueberry topping have cooled, top the pie with the blueberry topping. Serve immediately or continue to refrigerate, covered, for up to 1 day. Serve with a dollop of whipped cream or ice cream on top, if desired.
Note: If pie is refrigerated for more than 1 or 2 hours, allow to sit at room temperature a few minutes before serving.
Yield: 8 servings