Preheat the oven to 350 degrees F (175 degrees C).
Place the blueberries into an 8x8 inch square baking dish. In a medium bowl, cream together the margarine and 3/4 cup sugar until smooth. Stir the flour into the creamed mixture alternately with the milk. Spoon batter over blueberries.
Mix together the remaining 3/4 cup sugar with the cornstarch and nutmeg. Sprinkle over the top. Pour boiling water over the whole thing.
Bake for 1 hour in the preheated oven.
Cool for at least 10 minutes to set. Serve with whipped topping or vanilla ice cream