Soak the urad dal and dalia separately for 1 hour.
Grind the urad dal first into very very smooth paste adding enough water.Do not add water at once. Add it in intervals.
Drain dalia completely as it would have absorbed lot of water. After draining ,add only half quantity (ie 1 glass ) of soaked dalia to the urad dal batter.Grind it to a coarse paste for about 10 mins along with urad. When done, transfer the batter (urad +dalia mix) to a large container.At this stage, add the remaining leftover soaked dalia ( ie 1 glass ) to the batter. Don't grind. This will give nice texture to the idli.Add salt and mix well. Set aside overnight / 6-8 hrs for fermentation.
Morning the batter would have fermented well. Mix well before pouring into greased idli moulds.
Heat water in a steamer.Grease idli molds with oil .Pour the batter into idli stand.
Steam for 12-15 mins on medium flame.Prick a tooth pick,if it comes clean it means its done.Allow it to cool a bit and remove from molds using a spoon or knife.
Thats it soft, spongy and healthy Dalia Idli's are ready to serve. Serve with Chutney / Sambar / Gojju / Chutney Powder.
If you don't like raw smell of broken wheat, instead of soaking you can roast it till they are aromatic.Later powder a bit and add to the urad batter.
You can temper the batter too for some spiciness or some finely grated or chopped veggies.