Prepare the Blackberry Filling:

1. Preheat your oven to 375°F (190°C).
2. In a large bowl, combine the blackberries, sugar, cornstarch, lemon juice, vanilla extract, cinnamon (if using), and salt. Toss to coat the blackberries evenly.
3. Transfer the blackberry mixture to a greased 8×8-inch baking dish or a similar-sized ovenproof dish.

Make the Biscuit Topping:

1. In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
2. Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs.
3. Stir in the buttermilk until just combined; the dough will be slightly lumpy.

Assemble and Bake:

1. Drop spoonfuls of the biscuit dough over the blackberry filling, covering most of the surface but leaving some gaps.
2. Bake in the preheated oven for 35-40 minutes, or until the topping is golden brown and the filling is bubbling.
3. Allow the cobbler to cool slightly before serving.

Serve:

• Serve the blackberry cobbler warm, with a scoop of vanilla ice cream or a dollop of whipped cream, if desired.