In Kanpur, we shifted into an apartment in 1993 and our neighbours there had a hing (asafoetida) factory. We first ate this achaar (pickle) at their house and since then it has been a staple in our house as well.
Peel and slice the mangoes. Scrape it off the guthli (seed) as much as possible. Chop mangoes into medium thin wedges of approximately the same size.
Put the wedges in a jar with salt and sun them for a day to sweat out the water (Day 1).
Now add the red chilli powder and sun it again for a day (Day 2).
On Day 3, add the hing. Stir it well. Sun it for the next two days (Days 3, 4, and 5).
On Day 6, top it with sugar/jaggery. Don’t mix it but let it sit like a layer on top. When you put it out in the sun, this will seep in slowly.
Sun it for 7 to 10 days with a cloth tied on the mouth of the jar.
Room temperature
When you add the sugar/jaggery, the mangoes will stop softening. So, check for required softness before adding the sweet ingredients; the mangoes should be at least halfway as soft as you want.
I also add sendha namak & a bit of kala namak (both are kinds of rock salts). It gives a totally different flavour and is good for digestion.
Do not mix in the sugar/jaggery. It has to layer on top and then seep in slowly.
Be very careful not to use a wet spoon to stir it or even wet hands while handling the pickle.