Preheat the oven to 375° F.
Put the berries into a deep-dish pie plate or bakign dish. Stir together the sugar and cornstarch, sprinkle over the berries and gently toss to combine. Slide into the oven for 20 minutes while you make the dumpling batter.
In a medium bowl, stir together the flour, sugar, baking powder and salt. In a small bowl or measuring cup, stir the milk and egg together with a fork. Add to the dry ingredients and stir just unilt you have a sticky dough.
Remove the pan from the oven, give the berries a quick stir, and drop large spoonfuls of the dumpling batter over the surface. Return to the oven for 20 minutes, or until the dumplings are golden and the fruit is bubbly.