Dry roast fenugreek seeds in a pan for 30 - 35 seconds, avoid over browning; let it cool. Grind it and Keep it aside
In medium flame add 2 tablespoon oil to the pan. When oil is hot add mustard seeds and and let it splutter. Add hing and give a quick mix
Turn the flame to low and add grated mangoes
Give a quick sauté and add turmeric powder and cook 2-3 minutes stirring once in a while
Add chilli powder and salt to it and continue cooking till the oil separates, stirring once in a while
In between cooking add remaining oil in regular interval and keep stirring
In between cooking add remaining oil in regular interval and keep stirring
When oil starts oozing out from the pickke and thooku comes together as a mass add fenugreek powder and mix well
Cook for a minutes and switch offMove the pan aside from the stove
After the thokku is completely cool put the thokku to airtight container