1. Thaw frozen blueberries in colander set over bowl to catch juices. Transfer juices (you should have about 1 cup) to small saucepan; simmer over medium heat until syrupy and thick enough to coat back of spoon, about 10 minutes.

2. Adjust oven rack to lower-middle position and heat oven to 375 degrees.

3. For the filling: Stir sugar, cornstarch, cinnamon, and salt together in large bowl. Add berries, with syrup, and mix gently with rubber spatula until evenly coated; add lemon zest and juice and mix to combine. Transfer berry mixture to 9-inch glass pie pan, place pie pan on rimmed baking sheet, and bake until filling is hot and bubbling around edges, about 30 minutes.

4. For the biscuit topping: Whisk flour, cornmeal, 1/4 cup sugar, baking powder, baking soda, and salt in large bowl to combine. Whisk melted butter, buttermilk, and vanilla in small bowl. Mix remaining 2 teaspoons sugar and cinnamon in second small bowl and set aside. One minute before berries come out of the oven, add wet ingredients to dry ingredients; stir with rubber spatula until just combined and no dry pockets remain.

5. To assemble and bake cobbler: Remove berries from oven; increase oven temperature to 425 degrees. Pinch off 8 equal-sized pieces biscuit dough and place on hot berry filling, spacing them at least 1/2 inch apart (they should not touch). Sprinkle each mound of dough with cinnamon-sugar. Bake until filling is bubbling and biscuits are golden brown on top and cooked through, 20 to 22 minutes. Cool cobbler on wire rack 20 minutes and serve.

1. Place fruit mixture in pie plate, set plate on rimmed baking sheet, and bake until hot and bubbling around edges, about 25 minutes.	2. Pinch off eight equal-sized pieces biscuit dough and place on hot berry filling, spacing them at least 1/2 inch apart.
3. Sprinkle each mound of dough with cinnamon-sugar. Bake until biscuits are golden brown on top and cooked through, 15 to 18 minutes.