Peel the kairi / raw green mangoes and place with 1 litre of water in a stainless-steel pot.
Bring to a boil, and then cook on low simmer till the kairi / raw mango is soft. This will take about 20 – 25 minutes.
Remove the kairi / raw mangoes and remove as much as pulp as possible, discarding the seed. Blend the kairi / raw mango pulp with water using an immersion blender. Or let the mixture cool, and then blend in a blender.
Place the blended kairi / raw mango mixture in the stainless-steel pot again, and add sugar.
Cook on low heat till the sugar dissolves, and the mixture thickens. This will take about 20 minutes.
Turn off the heat, and then add the roasted cumin powder along with the black salt. Stir through.
Let the mixture cool, and then store in the refrigerator in clean bottles. Alternately, the aam panna / kairi sharbat can also be frozen in trays. Once the panna / sharbat is frozen, then the ice cubes can be kept in a ziploc bag.