The name Paal Appam also called VellaAppam in some parts of Kerala
In a big bowl add rice flour and water ,mix well ..
Soak aval in half cup of lukewarm water for 15 minutes ..Then grind to a fine paste ..to that add yeast ,sugar and salt and again grind..
Add this paste to the rice flour batter and mix well..
Check the taste and adjust .. close the bowl and allow to ferment in a dry warm place ..
After the fermentation make appam ..