Take rava in pan and in medium flame with constant stirring roast it for few minutes. Transfer it to a bowl and let it cool down.
Next add grated coconut, green chilly and cumin in to a mixer jar. Make a fine paste adding required water.
Trim the edges of cucumber and chop it very finely. You can even grate it. Add cucumber and ground coconut paste to rava.
Add salt to it and mix everything well. Then add 1/2 cup of water to the bowl and mix such that everything comes together like loose dough.
Ensure it doesn't turn too watery or stiff. Consistency is somewhere between dough and batter. Cut the banana leaf in to small pieces and take a limp of dough.
Spread the dough over banana leaf, fold the ends together and steam it in idli steamer.
Continue this process with rest of the dough. Steam it for 10-15 minutes or till done.
Aromatic and tasty cucumber rava idli is ready to serve with spicy coconut chutney.