1. Soak separately Blackgram dal in water for about 2-3 hours. Also soak Toor dal, fenugreek seeds and raw rice together in water for about 2 -3 hours. Soak par boiled rice in water for about 5-6 hours since it needs to soften to grind in the mixer/grinder.
2. Grind Blackgram Dal in the wet grinder adding water in steps to a fine consistency.
3. Grind soaked Toor dal, soaked raw rice and fenegreek seeds in the mixer together adding water in steps to a fine but thick consistency.
4. Grind soaked Par-boiled rice in the mixer separately to a fine and thick consistency. Add ground Toor dal-raw rice mix from step-3, ground par-boiled rice from step-4 to the ground dal from step-1 and run the grinder to mix up and the mixed dosa dough is as shown in the image below.
5. Transfer it to a broad bowl , add salt and allow it to ferment overnight.
6. Next morning on fermenting dosa dough would be as below.
7. Place a dosa skillet on medium flame and on heating, add in a little butter on it and rub it with a coconut coir/Tissue paper so that it spreads to the whole skillet evenly.
8.Splash some water simmering the flame and pour a laddle of dosa dough and spread it to a medium thickness. Put the flame on high and close it with a lid adding 1/4 teaspoon butter on the dosa..
9. Serve hot with chutney and potato special mix.