The difference between Kolkata biryani and other biryani are 1) Kolkata biryani has subtle flavors. This biryani is cooked with a few aromatic spices. It is less spicy compared to other biryani. 2) Potatoes are added to this biryani that making it unique. 3) Another difference is the addition of Khoya to the biryani. 4) Mustard oil is used to make this biryani.