Heat oven to 350°. Place 1/2 cup butter or margarine in an 8" square pan and put in oven until melted. Meanwhile, combine 3/4 cup sugar, 1 cup self-rising flour (which I don't have, so I added a touch of baking powder and salt to my regular flour), and 3/4 cup milk. Pour over melted butter and top with about 2 cups blackberries. Return to oven and bake for about 45 minutes.