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 1/2 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. 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.