– 2 pie crusts , homemade or store-bought – 5 cups (725 grams) pitted and halved fresh dark sweet cherrie – 2/3 cup (135 grams) granulated sugar – 3 tablespoons (21 grams) cornstarch (or cornflour) – 2 teaspoons fresh lemon juice – 1 teaspoon pure vanilla extract – 1 tablespoon (15 grams) butter , cut into small piece – 1 large egg – 1 tablespoon (15 ml) milk – Coarse sugar to sprinkle on top (optional)