In a medium bowl, whisk together the flour, granulated sugar, baking powder, and salt. With a pastry blender, 2 knives used scissor style, or your hands, blend in 1/2 C butter until crumbly. With a fork, stir in egg and mix just enough to blend. Add heavy cream and mix just to incorporate; do not overmix.
Preheat oven to 350 degrees. Lightly grease a 9-inch cake pan, line the bottom with waxed paper, and grease the paper.
Press the dough evenly into the bottom of the cake pan. Place the blueberries on top of the dough and sprinkle with the brown sugar. Place the remaining butter pieces over the berries.
Bake for 20 to 25 minutes, or until golden brown. Cool on a wire rack. Remove the cake from the pan, cut in wedges, and serve with raspberries, blackberries, and strawberries.