For the filling: Butter the sides and bottom of the insert of a 6-quart slow cooker. Whisk together the cornflour, lemon juice and 2 tablespoons water in a small bowl. Add the mixture to the insert, add the berries and granulated sugar and toss.
For the biscuit topping: Whisk together the flour, 2 tablespoons of the granulated sugar, baking powder and salt in a large bowl. Add the butter and rub the mixture together with your fingers so that it forms a coarse meal with some pea-sized lumps. Add the milk and stir with a wooden spoon to form a wet dough.
Drop spoonfuls of the dough on top of the berry mixture. Combine the remaining 1 tablespoon granulated sugar and the cinnamon and sprinkle over the dough. Cover the slow cooker and set to high for 3 to 4 hours. The cobbler should be bubbly and the biscuits should be cooked through. Let rest for 20 minutes before serving.
For the sour cream topping: Meanwhile, combine the double cream, sour cream and icing sugar in a medium bowl and beat with an electric mixture until the mixture forms medium peaks.
Spoon the cobbler into bowls and top with the whipped sour cream topping.
Copyright 2013 Television Food Network, G.P. All rights reserved