Put skinless green gram in a non-stick pan, add half cup castor sugar and one cup water and bring it to a boil. Cook till the green gram is done. Remove from heat, cool and grind to a smooth paste.
Put rice flour in a bowl, add potato, remaining castor sugar and half cup water and knead into soft dough. Cover and set aside for ten to fifteen minutes.
Mix refined flour and half cup water in a small bowl till smooth.
Spread sesame seeds on a plate. Heat sufficient oil in a kadai.
Divide dough into eight equal portions, shape them into balls and flatten them. Make a dent in the center of each ball and stuff with ground paste. Bring the edges together and press lightly to seal. Shape them into balls again.
Dip these dumplings in refined flour mixture and roll them in sesame seeds.
Gently slide them into hot oil and deep-fry till crisp and golden. Drain on absorbent paper.
Arrange the dumplings on a serving plate and serve warm.