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 pinch of salt. Toss until berries are evenly coated. Spread mixture in prepared baking dish.
03 - In a separate bowl, whisk together flour, sugar, baking powder, baking soda, and salt until well combined.
04 - Pour melted butter, milk, and vanilla extract into flour mixture. Stir gently until just combined—batter will be thick. Avoid overmixing to prevent tough texture.
05 - Drop spoonfuls of batter evenly over blueberry filling, covering most of surface. Leave small gaps between dollops to allow fruit juices to bubble through during baking.
06 - Bake for 40-45 minutes until topping is golden brown and set, and berry filling is bubbling around edges. Insert toothpick into center of topping to confirm doneness.
07 - Let cobbler cool for at least 15 minutes before serving. This allows filling to set slightly. Serve warm with vanilla ice cream or whipped cream if desired.