1. Preheat oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish.

2. Prepare apples: peel, core, and thinly slice the Granny Smith apples.

3. Make the filling: in a large bowl, combine sliced apples, granulated sugar, brown sugar, flour, cinnamon, nutmeg, salt, lemon juice, and vanilla; toss until apples are evenly coated.

4. Transfer the apple filling to the prepared baking dish and spread into an even layer.

5. In a separate bowl, whisk together the flour, granulated sugar, baking powder, and salt for the topping.

6. Cut in the chilled cubed butter with a pastry cutter or your fingertips until the mixture resembles coarse crumbs.

7. Stir in the cold milk and vanilla extract just until a soft dough forms; do not overmix.

8. Drop spoonfuls of the dough evenly over the apple filling, leaving a few small gaps for steam to escape.

9. Sprinkle the top with turbinado or coarse sugar, if using, for extra crunch and sparkle.

10. Bake for 40–50 minutes, or until the apples are bubbling and the topping is golden brown and cooked through.

11. Remove from the oven and let the cobbler cool for 10–15 minutes to allow the filling to thicken slightly.

12. Serve warm, optionally topped with vanilla ice cream or whipped cream.