Preheat the oven to 350°F.
Combine the berries and 2 cups of the sugar in a large, deep pot over medium heat. Cook, stirring occasionally, until a syrup forms, about 10 minutes. Remove 1/2 cup of the hot berry juice and dissolve the cornstarch in it. Return this to the berry mixture and stir until the mixture thickens, then remove from the heat.
Combine 1/2 cup (1 stick) of the butter, the remaining 1 1/2 cups sugar, and the eggs in a large mixing bowl and mix until smooth. Add the vanilla and stir to blend.
Sift the cake flour, baking powder, and salt into another large mixing bowl. Add the butter mixture and water. Stir to blend.
Smear the remaining 4 tablespoons (1/2 stick) butter over the bottom of an 18x12x2-inch baking dish. Pour the berry mixture into the dish. Spoon the batter, about 2 tablespoons at a time, to form drop biscuits or dumplings over the top of the berry mixture. Bake until the dough is golden and the mixture bubbles, 55 minutes to I hour.
Scoop a large spoonful of the berries with a biscuit into each dessert bowl. Serve with ice cream, if you wish.
Makes about 20 small servings.
Recipe from "Eula Mae's Cajun Kitchen Cookbook"