Heat oil in a medium pot over medium heat. Add the onion and cook for 5 or so minutes, until cooked through and translucent.
While onion is cooking, combine all the spices in a small bowl (makes them easier to add!).
Add the ginger, garlic and spices to the pot and cook for a minute, until nice and fragrant.
Add the celery, sweet potato and stock (just enough to barely cover the veggies).
Bring to a boil, reduce heat and simmer for 15 or so minutes, until sweet potato is cooked through.
Stir in the coconut milk, then puree with an immersion blender.
Taste for spice and salt and add more as needed (you could kick it up with some cayenne if it's not spicy enough for you).
