Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.

Prepare the filling: In a large bowl, gently toss the peach slices with 3/4 cup sugar, cornstarch, vanilla extract, cinnamon, and lemon juice until evenly coated. Pour the peach mixture into the prepared baking dish and spread into an even layer.

Prepare the topping: In a separate medium bowl, whisk together the flour, 2 tablespoons sugar, baking powder, and salt. Cut in the cold, cubed butter using a pastry blender or your fingertips until the mixture resembles coarse crumbs.

Pour the 1/2 cup milk into the flour mixture and stir gently until just combined into a shaggy dough. Do not overmix. Drop spoonfuls of the dough evenly over the peach filling. It should cover about 75% of the surface, leaving gaps for steam to escape.

Brush the tops of the dough dollops lightly with the remaining 1 tablespoon of milk and sprinkle generously with turbinado sugar for a crisp crust.

Bake for 40-45 minutes, or until the topping is golden brown and the peach filling is bubbling thickly around the edges. If the edges brown too quickly, cover loosely with foil.

Let cool for at least 15-20 minutes before serving warm. Serve with a scoop of high-quality vanilla bean ice cream or fresh whipped cream.