Preheat your oven to 375°F. In a 9x13-inch baking dish, combine the blackberries with 1/2 cup granulated sugar, 2 tablespoons cornstarch, and 1 tablespoon fresh lemon juice. Toss gently to coat the berries evenly and spread them out in the dish.

In a medium bowl, whisk together 1.5 cups all-purpose flour, 2 tablespoons granulated sugar (for the topping), 2.5 teaspoons baking powder, and 1/2 teaspoon kosher salt. Cut the cold, cubed unsalted butter into the dry ingredients until the mixture looks like coarse crumbs. Pour in 3/4 cup buttermilk and stir just until a shaggy dough forms.

Use a spoon to drop dollops of the biscuit dough evenly over the blackberry mixture. The dough pieces don’t need to cover all the fruit; gaps are fine. Sprinkle a bit of coarse sugar over the biscuit topping for a crunchy finish.

Place the cobbler in the preheated oven and bake for 32 to 35 minutes. Watch for the biscuit topping turning a golden brown and the blackberry filling bubbling up at the edges.

Once baked, remove the cobbler from the oven and let it cool for about 10 minutes. This rest time helps the filling thicken slightly.

Serve warm topped with a scoop of vanilla ice cream for a truly special treat.

Store any leftover cobbler in an airtight container and keep it in the fridge for up to 4 days. Reheat gently in the microwave for 30 to 45 seconds before serving.