Preheat your oven to 350°F (175°C).
In a large bowl, combine blueberries, 1/2 cup sugar, cornstarch, lemon juice, and vanilla extract.
Pour the blueberry mixture into a greased baking dish.
In another bowl, whisk together flour, baking powder, salt, and remaining sugar.
Add milk and melted butter to the dry ingredients, mixing until just combined.
Drop spoonfuls of the biscuit batter over the blueberries.
Bake for 40-45 minutes, or until the topping is golden brown.
Let cool for a few minutes before serving.
Serve warm with ice cream or whipped cream.