3 Tablespoons cornstarch
1/2 cup granulated sugar
6 cups picked over blueberries
2 Tablespoons fresh lemon juice
1 1/2 cups all-purpose flour
1/2 cup firmly packed light brown sugar
1 1/2 teaspoons double-acting baking powder
3/4 teaspoon salt
1 teaspoon cinnamon
1 stick (1/2 cup) cold unsalted butter, cut into bits
In a large bowl stir together the cornstarch and the granulated sugar.
Add the blueberries and the lemon juice to the cornstarch and sugar.
Toss the mixture until it is combined well and transfer it to a buttered 10-inch (6-cup) deep-dish pie plate.
In a bowl combine well the flour, the brown sugar, the baking powder, the salt, and the cinnamon, add the butter, and blend the mixture until it resembles coarse meal.
Sprinkle over the blueberry mixture. If the topping looks dry, then add small cubes of butter to the top.
Bake the cobbler on a baking sheet in the middle of a preheated 400°F. oven for 30 to 40 minutes, or until the topping is golden and cooked through.