After soaking for 4 hours fenugreek seeds would have doubled in volume, add them in to mixer or wet grinder and grind them in to fine paste. Include water as required and grind.
When the fenugreek seeds are finely ground, drain the soaked rice and include it. Adding a cup of water, grind both of them together in to fine batter. Ensure the batter is not very thin. It should be little thicker than normal dosa batter.
Let the batter rest and ferment for at least 12 hours. This batter takes more time to ferment. So give enough time. After fermenting, the batter is porous and thick.
Heat a dosa griddle and smear some oil on it. Take ladle full of fenugreek dosa batter and spread in circular motion in the form of dosa. Let cook for 2 minutes and slowly remove from the griddle using spatula. Repeat the process with rest of the batter.
Porous and soft fenugreek dosa is ready to serve with chutney and tiffin sambar.