01 - Preheat oven to 375°F. Lightly grease a 9x9-inch baking dish with butter or cooking spray.
02 - In a large bowl, combine frozen blueberries, granulated sugar, cornstarch, lemon juice, ground cinnamon, and salt. Toss until berries are evenly coated. Pour mixture into the prepared baking dish and spread into an even layer.
03 - In a medium bowl, whisk together flour, sugar, baking powder, baking soda, and salt until well combined.
04 - Add melted butter, whole milk, and vanilla extract to the flour mixture. Stir gently until just combined; the batter will be thick and slightly lumpy. Avoid overmixing.
05 - Drop spoonfuls of batter evenly over the blueberry filling, covering most of the surface. Leave small gaps between spoonfuls to allow the fruit mixture to bubble through during baking.
06 - Bake for 40 to 45 minutes until the topping is golden brown and set, and the berry filling is bubbling around the edges. The topping should feel firm when lightly touched.
07 - Let the cobbler cool for at least 15 minutes before serving to allow the filling to set slightly. Serve warm with vanilla ice cream or freshly whipped cream.