Preheat the oven to 325 degrees F.
Place the peaches in a 9-by-9-inch baking pan. In a medium bowl, mix together the flour, 3/4 cup of the sugar, the baking powder and 1/2 teaspoon of the salt. Add the milk and melted butter and mix well. Pour the batter evenly over the peaches.
In a small bowl, mix together the remaining 1/4 cup sugar, the cornstarch and remaining 1/2 teaspoon salt. Sprinkle the mixture over the batter. Evenly pour the boiling water all over.
Bake until golden brown and bubbling, 50 minutes. Serve in individual dessert dishes with vanilla ice cream or whipped cream, if desired.