Start by cutting an X on the bottom of the peaches. Bring a pot of water to a boil and dip whole, unpeeled peaches into the water for about 60 seconds (75-90 seconds at high altitude). Then immediately plunge the peaches into ice water. After about 10 seconds, remove the peaches from the water and use a paring knife or your finger to peel the skin away — it should practically peel itself!
Preheat the oven to 425° F
In a large bowl, combine the sliced peaches, 1/4 cup white sugar, 1/4 cup brown sugar, 1/4 teaspoon cinnamon, nutmeg, lemon juice, and cornstarch. Toss to coat evenly. Pour into a 2-quart baking dish and bake for 10 minutes.
Meanwhile, in another bowl combine the flour, 1/4 cup white sugar, 1/4 cup brown sugar, baking powder, and salt. Cut in the chilled butter with your fingertips or a pastry blender until the mixture resembles coarse crumbs. Stir in the boiling water until just combined.
Remove the peaches from the oven. Drop spoonfuls of the topping evenly over the peaches.
Mix the remaining 3 tablespoons white sugar with 1 teaspoon cinnamon and sprinkle over the entire cobbler.
Bake for about 30 minutes, or until the topping is golden brown and the fruit filling is bubbling around the edges.
