Combine dry ingredients: Whisk cornmeal, flour, baking powder, cinnamon and salt together in a medium bowl. Whisk well.
Add butter and milk: Cut in the butter until you have a bowl full of small crumbs. Add the buttermilk and stir JUST until combined. Do not overmix! Chill for 10 minutes in the fridge.
MAKE THE FILLING:
Preheat the oven to 400°F.
Combine all ingredients for the filling in a deep 7x11 rectangular baking dish.
FINISH THE COBBLER:
Drop the biscuit mix all over the filling. Sprinkle evenly with the remaining brown sugar.
Bake for 25-30 minutes, or until the biscuits are puffy and golden, and the filling is bubbly.
Allow to rest for 5-10 minutes before serving.
Very sweet peaches will need little to no extra sugar. More tart peaches may need even more than specified in the recipe.Very juicy peaches need less water to help make a nice and juicy filling. If your peaches are still very firm, you will need more water to make a bubbly filling vs if your peaches are very ripe and juicy.