Cut two sizes of pastries from the dough: one is 15 cm. in diameter, and the other is about 13 to 12 cm.
Brush the 15-cm pastry with egg white, then add 2 teaspoons of the cooled white sauce.
Add at least 2 teaspoons of tomato sauce, season with salt and pepper, and at least 2 teaspoons of grated mozzarella.
Use the smaller circle of pastry to cover and seal the sides by pressing with your fingers.
Place each covered Rustico pastry in a baking tray lined with baking paper.
Place the tray in the refrigerator for at least 60 minutes to chill, uncovered.
Preheat the oven to 200°C (375°F).
Remove the tray from the refrigerator and brush the pastries with the remaining egg white.
Place the tray in the oven for 20 to 25 or until they turned golden in color.
Serve and enjoy your Rustico Leccese!