Rinse the idli rice and urad dal separately.

Soak the idli rice and fenugreek seeds together in a bowl with enough water for about 4-6 hours.

Soak the urad dal in a separate bowl with enough water for the same duration.

Drain the water from the soaked urad dal and grind it in a blender or wet grinder with a little water until it becomes a smooth, fluffy batter. This may take around 15-20 minutes.

Drain the water from the soaked idli rice and grind it to a slightly coarse texture. The texture should be finer than semolina but not as fine as flour.

Mix the urad dal batter and the idli rice batter together in a large bowl. Add salt and mix well. The consistency should be similar to pancake batter.

Cover the bowl and let the batter ferment in a warm place for 8-12 hours or overnight. The batter should rise and become airy.

After fermentation, mix the batter gently. If it's too thick, add a little water to achieve the right consistency.

Heat oil in a pan. Add mustard seeds, urad dal, chana dal, curry leaves, and chopped green chilies. Sauté until the dal turns golden brown.

Add this tempering to the idli batter and mix well.

Grease the idli molds with oil.

Pour the batter into the molds.

Steam the idlis for about 12-15 minutes or until a toothpick inserted comes out clean.

Allow the idlis to cool for a few minutes before removing them from the molds.

Serve hot with coconut chutney, tomato chutney, or any chutney of your choice.