Dry roast the oats for a few seconds. When cool, grind into a fine powder and keep aside. Heat oil in a pan and saute the semolina for a minute.
Now add the powdered oats, salt and enough buttermilk to make a batter like consistency. Just before steaming, add the eno fruit salt and a little water. Mix well. Spoon the batter on to greased idli moulds.
Steam for 15-20 minutes. (If using a pressure cooker, do not put the vent). When cool, demould them and make a hole in the centre with any bottle lid or a cookie cutter.
Smear some coconut chutney / mayo / sauce over the idlis.
Sprinkle all the toppings as desired. Serve as it is or with coconut chutney and sambar.
