For the batter • blueberries (about 125 g) • all-purpose flour (about 180 g) • butter (softened, about 60 g) • milk (about 100 ml) • brown sugar (about 80 g) • baking powder • eggs • For the topping • all-purpose flour (about 20 g) • brown sugar (about 20 g) • butter (cold, about 15 g)