In a medium bowl, whisk flour, the remaining 2 tb granulated sugar, baking powder and salt to combine. Using a pastry blender or two knives, cut in the butter until the mixture resembles coarse meal. In small bowl, beat milk and egg together. Stir into flour mixture to form a soft dough. Turn the slow-cooker setting to HIGH. Drop the dough by tablespoonfuls on top of the blueberries. Cover and slow-cook until the topping is firm and a toothpick inserted in the center comes out clean, about 30 minutes. Sprinkle the dumplings with the brown sugar. Let the grunt stand for 5 minutes before serving, then spoon into individual bowls.