Preheat the oven to 350 degrees. Grease a 8x8 inch pan well with butter.
In a large bowl, stir the peach slices, brown sugar, cornstarch, lemon juice, lemon zest, ginger, cinnamon, and salt together until thoroughly combined.
Spoon filling into prepared pan and bake for 15 minutes.
Remove from the oven and then prepare the biscuit topping.
Prepare biscuit topping by whisking together flour, sugar, baking powder, baking soda, and salt together in a large bowl. Cut in the cold butter, using a pastry cutter, food processor, or two forks, cut the butter into the mixture until it resembles wet sand and the butter is about the size of peas.
Drizzle in the milk and gently mix until just biscuit dough is JUST combined--do not over mix!
Dollop dough all over peach filling.
Mix together the egg and remaining buttermilk.
Brush the top of the biscuit dough with egg wash and then sprinkle with granulated sugar.
Bake for 37-42 minutes, or until lightly browned and biscuit topping is cooked through.
Serve warm along with ice cream of whipped cream if desired.
Homemade Buttermilk--if you do not have buttermilk, you can easily make your own using milk of any kind. Simply add ½ teaspoon distilled vinegar or lemon juice to a mixing cup and pour in enough milk to equal ½ cup milk. Let sit for 5 minutes before using. (I let it sit in the refrigerator for the milk to stay cold for the biscuit topping.)If you need this Cobbler to be egg-free, simply brush the biscuit topping with milk instead of the egg wash. Your cobbler top won’t brown as well, but will still be beautiful and delicious!Using Frozen Peaches: Frozen peaches work really well in place of fresh peaches, simply defrost and drain off the juices before preparing the cobbler.Using Canned Peaches: To replace the fresh peaches, drain 45 ounces of canned peaches (or three 15-ounce cans) before proceeding with the recipe. You also can skip the step of pre-baking the peaches. Use tapioca starch in place of cornstarch if needed. Storage: Leftover peach cobbler can be stored covered in the refrigerator for 3-4 days. To reheat the peach cobbler, dish up the cobbler into individual servings and microwave for 30-45 seconds. Alternatively, heat the cobbler for 20 minutes in a 300-degree oven until warm.