Prepare the blackberries: In a large bowl, combine 2 1/2 cups fresh blackberries and 1 cup sugar. Stir gently and let the mixture sit for 25-30 minutes to allow the blackberries to macerate, releasing their juices and creating a delightful syrup.
Preheat the oven: Set your oven to 375°F (190°C) to ensure it’s ready for the cobbler when it’s time to bake.
Make the batter: In another bowl, combine 1 cup all-purpose flour, 2 teaspoons baking powder, 1/2 teaspoon salt, and 1 cup milk. Stir the mixture until thoroughly combined. Then, pour in 1 stick of melted unsalted butter and stir until the batter is smooth.
Assemble the cobbler: Grease a baking dish lightly (no need for excessive grease!) and pour the batter into the dish, spreading it evenly. This forms the base for the blackberry topping.
Add the blackberries: Carefully pour the macerated blackberries with their syrup over the batter, spreading them evenly on top. Do not stir; the blackberries will settle into the batter during baking.
Bake: Place the baking dish in the preheated oven and bake for 45 minutes to 1 hour or until the top is golden brown and the cobbler is set, with bubbling juices around the edges. A toothpick inserted into the center should come out clean.
Cool and serve: Once baked, remove the cobbler from the oven and let it cool for at least 15 minutes before serving, allowing the flavors to settle.