01 - Preheat your oven to 375°F. Lightly grease a 9x9-inch baking dish with butter or cooking spray.
02 - In a large bowl, combine the frozen blueberries, granulated sugar, cornstarch, lemon juice, ground cinnamon, and a pinch of salt. Toss until the berries are evenly coated. Spread the mixture evenly in the prepared baking dish.
03 - In a separate medium bowl, whisk together the all-purpose flour, 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 with a spatula or spoon until just combined. The batter will be thick—do not overmix.
05 - Drop spoonfuls of the batter evenly over the blueberry filling. Cover most of the surface but leave small gaps for the fruit juices 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 vigorously around the edges.
07 - Let the cobbler cool for at least 15 minutes before serving. Serve warm with vanilla ice cream or whipped cream for the best experience.