egg wash & topping: 1 large egg beaten with 1 Tablespoon buttermilk
2Tbspgranulated sugar mixed with ½ tsp ground cinnamon
Preheat the oven to 350°F (177°C) and grease a 9×13 inch pan.
In a large bowl, stir the peach chunks, brown sugar, cornstarch, lemon juice, vanilla, cinnamon, nutmeg, and salt together until thoroughly combined. Spoon filling into prepared pan and bake for 10 minutes. Remove from the oven and set aside as you prepare the topping. Keep oven on
Whisk the flour, sugar, baking powder, baking soda, and salt together in a large bowl. Add the butter. Using your hands or a pastry cutter cut the butter into the mixture until it resembles coarse meal (pea-sized bits). While slowly stirring with a fork, slowly drizzle in the buttermilk. Mix until evenly combined. Take handfuls of dough and gently flatten out. Place dough all over the top of the peach filling. It doesn’t need to be perfect or look pretty– some peach filling can be showing.
Brush the top of the biscuit dough with egg wash, then sprinkle with cinnamon-sugar.
Bake for about 45 minutes, or until lightly browned and biscuit topping is cooked through. (Stick a toothpick into the biscuit topping, if it comes out clean– it is cooked through and the cobbler is done.) Set the pan on a wire rack, then cool for 5 minutes before serving. Serve warm a la mode.