Adjust an oven rack to the lower-middle position and heat the oven to 375 degrees F (190 degrees C).
For the filling: Stir the Granulated Sugar (1/2 cup), Corn Starch (1 tablespoon) and Salt (1 pinch) together in a large bowl. Add the Fresh Blueberries (6 cup) and mix gently with a rubber spatula until evenly coated; add the zest of the Lemon (1) plus the juice from 1/2, and mix to combine.
Transfer the berry mixture to a deep 9-inch pie plate or 9x13-inch vessel. Place pan on a rimmed baking sheet, and bake until the filling is hot and bubbling around the edges, about 25 minutes.
Meanwhile, whisk the All-Purpose Flour (1 cup), Granulated Sugar (1/4 cup), Baking Powder (2 teaspoon), Baking Soda (1/4 teaspoon) and Salt (1/4 teaspoon) in a large bowl to combine. Cut Unsalted Butter (4 tablespoon) into small pieces and use your fingers to incorporate the butter into the mixture — it's ok if the butter gets soft.
Five minutes (longer is fine) before the berries come out of the oven, add the Buttermilk (1/3 cup) and Vanilla Extract (1/2 teaspoon) to flour mixture and mix to combine. Pat mixture into ball or rectangle and roughly divide into seven or eight pieces.
To assemble and bake the cobbler: Remove the berries from the oven; increase the oven temperature to 425 degrees F (220 degrees C). Drop the pieces of biscuit dough on the hot berry filling, spacing them about half inch apart. Brush biscuits with Milk (2 teaspoon) and sprinkle with Raw Cane Sugar (2 teaspoon).
Bake until the filling is bubbling and the biscuits are golden brown on top and cooked through 15 to 18 minutes.
Cool the cobbler on a wire rack 20 minutes (or less) and serve with Vanilla Ice Cream (to taste).