Wash and soak horse gram dal, urad dal, and idli rice separately for 5-6 hours.

Add methi seeds to the rice an hour before grinding.

Drain horse gram and grind into a thick, smooth batter.

Transfer the horse gram batter to a large vessel.

Drain rice and grind into a smooth paste.

Add the rice paste to the horse gram batter.

Grind the urad dal into a smooth, fluffy batter.

Add the urad dal batter to the horse gram and rice batter along with salt.

Mix well with hands and let it ferment at room temperature for 6-8 hours.

After fermentation, add water to adjust the consistency to that of an idli batter.

Pour the batter into greased idli molds using a ladle.

Place the idli plate inside the idli cooker.

Steam for about 10 minutes.

Check for doneness by inserting a toothpick or fork. If it comes out clean, the idli is cooked.

If not cooked, steam for a few more minutes.

Remove from the idli plate and serve.

Serve hot with coconut chutney or tomato chutney, and a cup of Kumbakonam filter coffee.