Peel and finely chop the onions and cloves of garlic. Core the chilli pepper, also finely chop. Peel and dice the sweet potatoes.
Briefly fry the onions in oil. Add the garlic, chilli and curry and fry briefly. Deglaze with the broth, add sweet potatoes and coconut milk. Bring to the boil briefly and simmer on a low flame for about 5 minutes.
Peel and slice the banana and add to the soup. Let it cook for another 5 minutes, then puree the soup (if it is too thick, just add more stock or coconut milk).