- 2 tablespoons cornstarch
- 1 1/2 cups plus 1 teaspoon sugar
- 1 1/4 lb blackberries (5 cups)
- 2 lb peaches (6 medium), peeled, pitted, and cut into 1/2-inch-thick wedges
- 3 cups all-purpose flour
- 1 tablespoon baking powder
- 1 teaspoon salt
- 2 sticks (1 cup) cold unsalted butter, cut into 1/2-inch cubes
- 1 cup plus 3 tablespoons whole milk
- Put oven rack in middle position and preheat oven to 425°F. Butter a 13- by 9- by 2-inch glass or ceramic baking dish (3-quart capacity).
- Whisk together cornstarch and 1 1/2 cups sugar in a large bowl, then add blackberries and peaches and toss to combine well. Transfer to baking dish and bake until just bubbling, 10 to 15 minutes.
- While fruit bakes, whisk together flour, baking powder, and salt in another large bowl, then blend in butter with your fingertips or a pastry blender until mixture resembles coarse meal. Add milk and stir just until a dough forms.
- Drop dough onto hot fruit mixture in 12 mounds (about 1/3 cup each), then sprinkle dough with remaining teaspoon sugar. Bake cobbler until top is golden, 25 to 35 minutes. Serve warm.