Dice the onions and fry them briefly in the oil. Also dice both types of potatoes and sweat them briefly, then add 1.5 l of boiling water and the coconut milk. As soon as the soup boils, add the lentils and then the carrots. Finely grate the ginger and add to the soup.
After about 15 - 20 minutes of cooking time, when the lentils are soft, stir in the finely diced mango and season the soup with broth, salt and, if you like, chilli flakes and a little curry or Asian spice.
I like soups that are creamy, so I pureed them briefly, but essentially left the pieces as they are. I also mixed red and yellow lentils, they have a similar cooking time. If you want to use other types, you just have to pay attention to a possibly longer cooking time!