Chop onion. Remove the skin from carrot and cut it into small pieces.
Slit green chilli lengthwise into two, chop ginger and mint leaves. Take a small piece of clean muslin cloth and put the chopped chilli, ginger and mint. Gather the corners of the cloth and tie with a thread and make a bundle.
Put both onion and carrot in a pressure cooker and add enough water to cover them. Place the cloth bundle in the cooker along with carrot. Add a pinch of salt and cook for two whistles. Allow to cool.
Open the lid and remove the cloth bundle. Squeeze the bundle on the cooked carrot, so that all the essence will come out. Put the carrot along with the cooked water in a mixie and grind it to a puree. Strain it. Put it in a vessel and bring to boil. Cook on medium flame till it slightly thickens or to a desired soup consistency.
Pour it in soup bowl and add required salt and pepper powder. Garnish with grated cheese or a dollop of cream. Or with simple bread croutons.
Note: If you like, you can fry the onion and carrot in a teaspoon of butter and then cook,