Preheat oven to 350 degrees F. Grease an 8x12 inch or 3 quart casserole.
Spread berries over the bottom of the baking dish and sprinkle with lemon juice.
In a mixing bowl, whisk together the flour, baking powder, salt and ¼ cup sugar. Cut in the butter with a pastry cutter or your fingers until coarse.
Add milk and stir just until soft and blended, then drop by small spoonfuls over the berries. Start with the edges and continue putting drops in the middle. Use the back of a spoon to spread the drops of dough into one thin layer covering berries.
Mix together the 1 ¼ cups of sugar and the 1 ½ tablespoons of cornstarch and sprinkle over the biscuit mixture.
Boil the water in the microwave or over the stove and pour water over the sugar as evenly as possible.
Bake at 350 degree for 50 minutes, then after 40 minutes raise the heat to 400 and bake for another 15 to minutes to help brown the topping.