Wash and soak urad dal and fenugreek seeds separately for 5 hours.
Wash and soak rice and whole wheat in a bowl for 5 hours.
Grind dal in a blender adding very little water at a time and grind till fluffy and light. Don't add too much water. Add little water at a time. Remove this to a bowl.
In the same blender, add rice and wheat and grind till smooth.
Add this to the urad dal, add salt and mix well till combined.
Now cover and leave this to ferment for 8 hours or overnight.
Now mix it gently.
Spoon this into idli moulds. Steam for 10 to 12 mins.
Remove and serve.
Video
Notes
Soak the grains for at least 4 to 5 hours.
Grind the urad dal in a blender till smooth and fluffy. Add little water at a time and keep mixing and keep grinding. Don't add too much water.
Grind urad dal till it gets light and fluffy which results in soft idlies.
You can grind them in a wet grinder instead of blender.
I usually soak the grains in the morning and grind the grains at night. Then leave to ferment overnight and use the batter the next day.
Grind the grains by adding very little water, the batter has to be little thick for soft idlies.
I used a traditional cloth idli steamer for steaming the idlies. If you are using regular idli cooker, grease the plates with little oil and steam cook.