Spoon the blueberries in the center of the pastry, leaving a 1 1/2-inch border all around. Fold the pastry border up and over the blueberries, pleating it as necessary. Brush the egg white on the pastry and sprinkle with sugar. Bake for about 55 minutes, until the pastry is golden brown and the filling starts to bubble. Transfer the baking sheet to a rack and let the tart cool to warm. Cut into wedges and serve warm or at room temperature.