In a bowl, mix grated potato, white cheese, 2 tbsp cashew, green chili, Chineses celery, 1/4 tsp cumin, salt, and ground black pepper. Mix well.
Add the flour, then mix well. Shape the potato mixture into balls.
Heat oil in a pan, and fry the potato mixture balls until brown.
For the sauce, saute onion in a pot for 5 minutes using the butter, after 5 minutes, add tomato, garlic, then mix again.
After mixing, season it with cardamom, laurel leaves, cinnamon, chili powder, turmeric powder, coriander powder, masala, and water. Stir for 5 minutes.
After 5 minutes, let it cool, then transfer it into a blender, blend the sauce mixture for 3 minutes. The heat it again for 5 minutes on the stove until thickened.
Transfer all the fried potato balls on a plate, then pour the sauce over the potato balls, and top with sour cream.
Serve hot and enjoy!