Rinse and soak rice and black gram (urad dal) for 5 -6 hours or overnight. Add fenugreek to the bowl of dal.
Drain out water and transfer to a powerful blender or vitamix and blend well.
Make sure to grind rice and dal separately.
Add less water while grinding as it won't be smooth if you add more water in this stage.
Add few ice cubes while grinding to maintain temperature of the batter.
High speed blender won't take more than 1 minute to grind.
Once perfectly done, transfer the batter to a large mixing bowl.
Adjust the consistency (flowing thick ) of batter by adding little water slowly and gradually mixing thoroughly.
Now add salt and mix it well (preferably with hands/ palms).
Now cover the vessel with a lid and transfer to a warm place or kitchen counter.
If required cover it around with a blanket or cloth to give the warmth.
Keep it for fermentation for around 8 -10 hours.
When the batter rises to double the original volume, take out required quanity.
Heat water in a steamer or cooker and bring it to boil.
Grease the molds lightly.
Now pour 1 tbsp of batter in each mould.
Place the mould stand inside steamer or cooker.
Conver with lid.
Remove whistle if using pressure cooker.
Steam on medium high heat for 12 - 15 minutes.
Turn off heat and wait for 2 minutes before opening the lid.
Open the lid carefully as it's full with steam and may hurt the hand.
Remove the stand and keep it aside for 5 minutes to cool naturally.
Then with help of a spoon remove the idli from moulds.
Serve idli with chutney or sambar.
Notes
Soak and grind the ingredients separately. You can also replace rice with idli rava or rice rava and reduce 1 step of the process.Use high power blender (Vitamix) or wet blender for large batch size.Take cold water or ice while grinding to stop overheating.While mixing batter, use hands to mix as it will get the natural heat of our body during the process. This will accelerate the fermentation process.Use salt before fermentation as it helps in fermentation and hinders over fermentation.Never use an airtight container for fermentation. Take stainless steel or ceramic ones.To refrigerate use a glass container preferably. Steel or plastic containers make it sour easily reducing its cell life. If storing in steel or plastic containers, use it in 2 days maximum.