To begin making Horsegram or Kollu Idli, wash and soak the horse gram, urad dal and idli rice separately for about 5-6 hours. Add Fenugreek seeds to the soaked rice around an hour before grinding. 

Drain the horsegram from water and grind into thick and smooth batter. Transfer it into large vessel. 

Now drain rice and grind into a smooth paste. Add it to the kollu batter.

Lastly, grind the urad dal to the grinder and grind it into a smooth and fluffy batter. Add it to the kolu and rice batter along with salt. 

Mix well using hands and keep it at room temperature for about 6-8 hours to ferment. After fermentation, add required water to adjust the consistency to that of an idli batter. 

Pour the batter into greased idli plate with ladle and place inside idli cooker.

Steam for about 10 minutes. To check if the Idli is cooked, you can insert a toothpick or a fork and if it comes out clean, it means the idli is cooked. If not, steam it for a few minutes. Remove from the idli plate and serve.

Serve Horse Gram Idli with Coconut Chutney or Tomato Chutney along with a cup of Hot Kumbakonam filter coffee