In a large pot, heat olive oil and butter. Add bay leaf and saute for 30 seconds. Then add onion, garlic, celery and fry till they turn soft.
Add ginger, carrot and fry for 3-4 minutes. Then add turmeric powder, cumin powder, coriander powder, red chilly powder and fry for another 1-2 minutes.
Now add 2 cups of vegetable stock or water and bring to boil. Once it comes to boil, simmer and cook for 25-30 minutes or until carrots are soft.
Remove the bay leaf. Using a stick blender, blend the soup until it becomes smooth. Or transfer to blender and blend in batches until smooth.
Return the soup to the heat and add remaining stock, salt and pepper. Simmer the soup to the desired consistency. Lastly stir in the lime juice.
Notes
The soup is little spicy from the ginger, red chilly powder and pepper. If you want less spice, reduce the ginger and skip the red chilly powder.
If the soup is too thick, add more stock or water and adjust to your desired consistency.
You can skip the butter and use olive oil instead.