Prep the mangoes - Wash and dry the raw mangoes thoroughly. Slice and roughly chop them, discarding the seed. (Ensure the chopped mangoes weigh 400 gms)
Transfer the chopped mangoes into a clean, dry, glass bottle. Add jaggery, salts, fennel powder, ginger powder, cumin powder, asafoetida, and mint leaves. Toss well.
Pour in 1.5 litres of boiled and cooled or filtered water. Shake well, then seal the bottle tightly. Cover with a cloth and keep it in a dark place away from sunlight for 3-4 days.
Once you see tiny bullets and a slight fizz, your aam panna is fermented.
Strain the liquid into clean, dry bottles, leaving 4 inch airspace. Seal and refrigerate for at least a day before serving. Shake gently and serve chilled. Refrigerate for upto 1 week.
Taste before refrigerating. Adjust salt or jaggery if needed.
Do not over ferment beyond 4 days in warm climate.
Always use a clean dry bottle to avoid spillage.