In a large pot, heat the oil over medium heat. Add the onions, celery, garlic, ginger, and carrots and sauté for 5-8 minutes.
Add the sweet potato along with the spices and stock, and give the mix a nice stir. Replace the lid and bring the soup to a boil, then turn it down and allow it to simmer on low heat for 30 minutes. Stir occasionally to make sure it isn’t sticking, and adjust the heat or add a little more water if it is.
Once the sweet potato is completely soft, take the soup off the stove and use a stick blender to blend until it’s smooth.