Soak the urad dal in warm water for 2-3 hours, then drain and grind it to a smooth, fluffy paste using minimal water. Set aside in a large mixing bowl.

Dry roast the rava in a pan over medium heat for 3-4 minutes until it turns aromatic and slightly golden. Transfer to a plate and let it cool completely.

Heat oil or ghee in the same pan and add mustard seeds. Once they splutter, add cumin seeds, curry leaves, cashews, ginger, and green chilies. Sauté until cashews turn golden brown.

Add the roasted rava to the tempering and mix well for 1 minute, allowing the semolina to absorb the flavors. Turn off the heat and let it cool for 5 minutes.

Transfer the tempered rava to the bowl with urad dal paste. Add yogurt, salt, and mix well to combine all ingredients thoroughly.

Gradually add water to achieve a thick, pourable batter consistency similar to pancake batter. Cover and let rest for 15-20 minutes at room temperature.

Meanwhile, grease the idli moulds with oil or ghee and set up your steamer with water. Bring the water to a rolling boil.

Just before steaming, add baking soda and Eno fruit salt to the batter. Mix gently in one direction until the batter becomes frothy and light.

Immediately pour the batter into greased idli moulds, filling each cavity about three-quarters full. Sprinkle chopped coriander on top.

Steam the idlis on high heat for 12-15 minutes until they're cooked through. Insert a toothpick to check; it should come out clean when done.

Turn off the heat and let the idlis rest in the steamer for 2 minutes. Remove and let cool for another minute before unmoulding. Serve hot with coconut chutney and sambar.