First prepare brining the tender mangoes/Uppumanga /Uppilitta Kannimang
See the method of preparation here
After having been in brine for 3 week
Now its time to make Pickle /Achar
In a frying pan, on a medium-low fire, dry roast the mustard seeds and the fenugreek /uluva seeds for a minute or so, remove from the fire and allow to cool
When cool, grind to a powder and keep aside
In same pan, add the red chilli powder and roast for couple of minutes
(Note - Care should be taken not to burn the spices while heating it, so keep stirring continuously
)Add the ground mustard / uluva powder to red chilli powder and combine well
Now pour the brine from the mangoes and bring to a boil remove from the fire
Adjust the salt and add more salt if needed
Let it cool
When the gravy has cooled down, add the gravy to mangoes in bharani /glass jar and shake and mix well
Heat sesame oil /gingely oil for a minutes remove from the fire; cool them and pour on top of the pickle
Tightly cover the mouth of jar with white cloth; close it with a lid and keep in a cool dark place for 2-3 month, atleast for 1 month
Then open and use whenever needed
Traditional Kerala style Kannimanga achar is ready
Serve and Enjoy with anything as you wish,Pairs well with curd rice or with rice gruel