Soft brown sugar gives a nice colour and flavour and if you do use it, make sure to break any lumps before you begin. If you don't have it you can simply use caster sugar. Demerara (granulated brown sugar) may also be used but you can pulse it in the mixie to give it a finer texture. If you don't have sour cream simple use a combination of hung curd and fresh cream. To make hung curd at home, just take 1 cup (250ml cup) thick yoghurt (curds) and place it in a thin muslin cloth. Tie up the loose ends and hang this bundle over your kitchen sink to allow the whey to drip off. You can also place the yoghurt in a fine mesh tea strainer instead of a muslin cloth. After about 45-50 minutes you will get thick, creamy curd. Add 3 teaspoons of fresh cream and mix well. Measure out 150 grams of this mixture and use it in the place of sour cream.