Heat butter in a pan and fry chopped onion and celery for few minutes till onions become translucent.
Add pumpkin pieces to the onions and add water just enough to the level of vegetables. Tie garlic, ginger, cumin and pepper in a muslin cloth. Put the bag in the vegetables. Transfer all these items into a cooker container and pressure cook on a slow fire for 8 about minutes.
When it becomes cool, remove the muslin bag and mash the vegetables will to a fine pulp and pass it through a sieve. Add water to get soup consistency. Mix corn flour in water and make it a thin paste. Add this paste to the soup to make it thicker. Add salt, pepper powder and mix well. Serve
