Step 1Heat the oven to 425 degrees.
Step 2Place the blackberries in a deep-dish pie plate (at least 3 inches deep). A deep pie dish will prevent the berry juices from overflowing in the oven. Sprinkle the berries with 1/2 cup of the sugar.
Step 3Combine the flour, baking powder and 1/4 cup of the sugar in a bowl. With your fingertips, blend in the butter completely. Stir in the half-and-half, being careful not to over-mix. Spoon the topping over the berries, not quite covering completely. Sprinkle with the remaining 2 tablespoons of sugar.
Step 4Bake until golden brown on top, 30 minutes. Cool the cobbler on a wire rack.