• Preheat the oven to 375°F.
• Lightly grease a 9x13 inch ceramic baking dish.

Blueberry Filling

• In a very large bowl stir together the blueberries, sugar, cinnamon, and lemon juice.
• Stir in the cornstarch to coat the berries. 
• Pour the berry mixture into the prepared pan.

Biscuit Layer

• In a medium bowl whisk together the flour, 1/4 cup sugar, baking powder, and salt. 
• In a large liquid measure cup or bowl, whisk together the melted butter, egg, milk, and vanilla extract. 
• Make a well in the middle of the dry ingredients, then pour the wet ingredients into the well.
• Stir the mixture together until combined - it will be thick. 
• Section off pieces of the biscuit dough (I usually do about ¼ cup) and flatten into circles about ½ inch thick. Cover the blueberry filling with the circles of biscuit dough. It doesn't need to completely cover the top of the berries. 
• Sprinkle the top with 1 tablespoon of sugar. 

Bake the Cobbler

• Cover the top of the pan with aluminum foil, and bake for 20 minutes.
• Remove the aluminum foil and continue baking for 20-25 minutes or until the top is golden brown and you can see the blueberries bubbling underneath.
• Remove from the oven and let cool for 15 minutes before serving.