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. Mix until the berries are evenly coated, then 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. Do not overmix as this can make the topping tough.
05 - Drop spoonfuls of the batter evenly over the blueberry mixture, covering most of the surface. Leave some small gaps for the fruit to bubble through during baking.
06 - Bake for 40 to 45 minutes, or 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. This allows the filling to set slightly. Serve warm with vanilla ice cream or whipped cream if desired.