2) In a large bowl, combine the blueberries and 100g of the sugar. Toss to combine and set aside.
3) In a medium bowl, combine the remaining 200g, the flour, and baking powder.
4) In a large bowl, beat the butter and milk together until smooth. Gradually beat in the flour mixture until smooth. Pour the batter into the prepared pan, then scatter the blueberries over the batter, letting them sink in, without mixing. Bake until the top is golden brown, 35 to 45 minutes. Let cool slightly before serving. Spoon the cobbler into bowls and top with ice cream and/or blueberries, if using.