01 - Preheat your oven to 375°F. Lightly grease a 9x9-inch baking dish with butter or cooking spray.
02 - In a large bowl, toss the frozen blueberries with granulated sugar, cornstarch, lemon juice, ground cinnamon, and a pinch of salt until evenly coated. Spread the mixture evenly in the prepared baking dish.
03 - In a separate medium bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt until well combined.
04 - Pour the melted butter, whole milk, and vanilla extract into the dry ingredients. Stir gently until just combined; the batter will be thick and slightly lumpy. Avoid overmixing to prevent a tough texture.
05 - Drop spoonfuls of the batter evenly over the blueberry mixture, covering most of the surface but leaving some gaps for steam to escape and fruit juices to bubble through during baking.
06 - Bake for 40 to 45 minutes until the topping is golden brown and cooked through, and the berry filling is bubbling vigorously around the edges.
07 - Allow the cobbler to cool for at least 15 minutes before serving to let the filling set slightly. Serve warm with vanilla ice cream or whipped cream if desired.