Preheat oven to 425°F and lightly grease a 9x13-inch baking dish.
In a large bowl, combine sliced peaches, 3/4 cup granulated sugar, brown sugar, cinnamon, nutmeg, lemon juice, and cornstarch. Toss gently and let sit for 10 minutes, then pour into prepared baking dish.
In a separate bowl, mix flour, 1/4 cup sugar, baking powder, and salt. Cut in cold butter using a pastry cutter or fork until mixture resembles coarse crumbs.
Stir in boiling water just until combined. Drop spoonfuls of batter over the peach mixture, leaving some gaps for steam to escape.
Bake for 40-45 minutes until topping is golden brown and fruit is bubbly around the edges.
Let cool for 15 minutes before serving warm with vanilla ice cream or whipped cream.