Using a fork, poke several holes in the sweet potato. Wrap the sweet potato in foil and roast it in the oven for 50 to 60 minutes, or until cooked through. If you are short on time, you can cook it in the microwave (see notes).
Add the oil to a large soup pot and heat to medium. Add the onion and garlic and saute until completely softened and browned, about 12 to 15 minutes. Add the spices and salt and saute for an additional 2 minutes.
Add the chopped kale leaves and cover the pot. Allow the kale leaves to cook and soften, about 1 to 2 minutes.
Scoop the flesh out of the sweet potato and add to the pot. Add the coconut milk and the vegetable broth, and bring to a simmer. Simmer for about 5 minutes.
Remove from heat and blend the soup inside the pot with an immersion blender until very smooth.
Season with more salt and pepper if desired.
Notes
If you can't find a large sweet potato, feel free to use two medium sized sweet potatoes.If you are short on time, cooking the sweet potato in the microwave is a good short cut. Poke holes in the sweet potato, and place it on a microwave safe plate. Microwave times will vary, but I would start with 5 minutes, then turn the potato over, and go for another 3-4 minutes. Store leftover soup in the refrigerator. It should stay fresh for about 3-4 days.