Soak Sama & Sabudana in curd for 3-4 hours.
Grind in a smooth paste. If batter is thick add some water. (it should be like normal Idli paste). Add rock salt. Keep 5-6 hours for fermentation.
Combine all ingredients of filling except oil & baking soda in a bowl. Mix well.
Form tikki shape.
Now add water in Idli steamer & let it boil. Meanwhile Grease Idli plate. Add baking soda or Eno in Idli batter. Mix well. Immediately pour one spoon Idli batter in Idli plate. Place one potatoes tikki.
Cover it by pouring one spoon Idli batter. Now keep it in Idli steamer. Steam it on high to medium flame (first 5 minutes high then medium). Switch off gas. Let it cool down.
De mould Idli & enjoy with coconut chutney
