Wash barley, urad dal and fenugreek. Soak them in water for at least 6 hours.
Once it is well soaked, grind the ingredients into a smooth paste, adding just enough water to make a fluffy batter. The batter should not be thin.
Remove, transfer the batter to a bigger bowl. The batter may rise during fermentation so give it a big enough bowl. If you are new to making dosas, place a plate under the bowl to collect any batter that may flow over.
Now place the batter in a warm spot to ferment. The fermentation may take 8-16 hours depending on where you live.
The batter is fermented when it smells slightly sour, ideally it should have risen as well.
Add salt and water as needed. The batter should be pourable consistency, similar to a pancake batter/regular dosa batter.
Heat a griddle/tava on medium-high heat and grease it with ghee or oil. Cast iron griddle is always ideal to make doses. When griddle heats up, pour a ladleful of batter right in the middle and spread it by moving your ladle in circular motion. Make a thin dosa.
Cover and cook. After 30 seconds remove the lid, spread oil or ghee on the dosa and continue cooking until done and it feels crispy.
As the dosa is spread thin, there is no need to flip the dosa and cook further. Using a thin spatula, gently peel the dosa off the griddle.
After each dosa, grease the griddle/tava with ghee/oil.