Preheat the oven to 375 degrees F and grease a 9x13in baking pan.
To make the biscuits, combine the flour, baking powder, salt, and butter in a food processor. Pulse 5-8 times or until pea-sized pieces start to form. With the food processor running on low, add the buttermilk. Once the dough just starts to come together, dump it on a floured surface. Pat the dough into a 1-inch thick rectangle. Cut into equal-sized squares (measuring about 1inx1in). Place the biscuits on a parchment paper-lined plate and place in the refrigerator. Meanwhile, whisk together the sugar and cinnamon. Set aside.
Now prepare the filling. In a large bowl, combine the peaches, 1/4 cup brown sugar, cornstarch, lemon juice, vanilla extract, 1/2 tsp cinnamon, nutmeg, and salt. Stir until evenly coated. Pour the mixture into the prepared pan.
Prepare the crumble by combining flour, remaining brown sugar, and butter in a small bowl. Using your hands, a fork, or a pastry cutter, work the mixture until coarse crumbs form (should be crumble-like). Sprinkle on top of the peach filling.
Brush the biscuits with melted butter and sprinkle with cinnamon-sugar. Place the biscuits on top of the filling and crumble. Bake the cobbler for 55min-1hour or until bubbly and the biscuits have browned. Remove from oven and let stand for 5 minutes before serving. Enjoy!