Wash and rinse rice. Soak it for 30 minutes in hot water.
Drain the water, and grind the rice, coconut along with salt and water to make the thick, finely coarse batter.
Mix in the cucumber. If the batter is too thick add in little water.
Heat the steamer. Let the water be hot. Grease the moulds. If you using instant pot, keep fill water, and turn to saute mode on.
Pour batter into the moulds. Fill them up until they are just full. Do not overfill them.
Place the moulds in the steamer, and steam them for 15-20 minutes. In instant pot, turn off saute mode, place the moulds in, turn on the steam mode, let it steam for 15-20 minutes.
Serve hot with coconut chutney.