• 300g unsalted butter, chopped
• 265g (1 3/4 cups) plain flour
• 50g (1/3 cup) self-raising flour
• 355g (1 3/4 cups, firmly packed) brown sugar
• 360g (1 1/2 cups) sour cream
• 300g white chocolate, finely chopped
• 2 x 500g pkts White Icing
• Pure icing sugar, to dust