FOR THE PEACH FILLING: – 5 cups (825 grams) sliced peache – 1/4 cup (50 grams) granulated sugar – 2 tablespoons (15 grams) cornstarch (or cornflour) – 1/2 teaspoon ground cinnamon FOR THE BISCUIT TOPPING: – 1 cup (125 grams) all-purpose flour , spooned & leveled – 1/3 cup (65 grams) granulated sugar – 1 teaspoon baking powder – 1/4 teaspoon ground cinnamon – 1/4 teaspoon salt – 3 tablespoons (45 grams) cold unsalted butter , cubed into small piece – 1/3 cup + 1 tablespoon (95 ml) milk – Coarse sugar or granulated sugar , for sprinkling on top (optional)