Preheat oven to 180 degrees C and grease a round baking dish with butter.
2
In a bowl, stir together the brown sugar, 25g granulated sugar, the flour, the baking powder and salt.Add the milk and the melted butter and whisk until smooth.
3
Pour all of the batter into the greased baking dish. Scatter the top with all of the blackberries.
4
Bake until the edges are golden and crispy, 50-60 minutes. When 10 minutes remain, sprinkle with remaining 25g granulated sugar.