In the same way as for the sweet Adai, dry roast the rice flour in a pan till a faint aroma emanates but do not brown.
In a largish pan, heat the oil and add the mustard seeds. Once they splutter, add the lentils and stir till they turn golden. Add the asafoetida, the chillies and the curry leaves and stir once or twice and then add the water. Make sure the asafoetida does not burn.
If you are using freshly powdered rice flour you might need a little less water, about 2 to 2 1/2 cups of water instead of the 3 cups for store bought flour. Bring the water to boil, and then add the cooked beans, the coconut and the salt. Now add the rice flour, and take the pan off the heat. Stir everything together taking care to break up the lumps of rice flour.
Place the pan back on the stove, and over medium heat, stir the mixture until the water is absorbed by the rice flour. Cook the dough till it keeps leaving the sides of the pan and coming to the centre as a thick ball. Take the pan off the heat and allow the dough cool to a temperature where it can be handled comfortably (warm but not cool)
Knead the dough by hand a couple of times so it is smooth and malleable. Pinch off bits the size of a small lemon and place on a greased square of plantain leaf or foil or even your greased left palm. Flatten the dough, with your fingers into a flat disc about 3-inch in diameter and 1/4- inch thick. Using you finger to poke a hole (about 1/2-inch big) in the centre so it looks doughnut-like.
Place it in your steamer. If flattening on your palm, like I did, place the flattened disc in one depression of a greased idli mould. Repeat with the remaining dough. Steam cook the "Adais", for about 10 to 12 minutes till they're well done. When cooked, they should not be sticky to touch. Let them cool, and then remove them.
Serve them with a small pat of fresh home-made unsalted butter. This recipe makes 25 to 30 Savoury Adais (of 3-inch diameter).