1. In a large shallow dish, spread rice and sprinkle with seasoned rice vinegar and sesame seeds.
2. Using a wooden spoon, toss gently to combine, (DO NOT STIR or rice will clump).
3. Keep rice covered with a damp cloth if not using immediately.
4. Using wet fingers, place a rounded teaspoonful of rice in the palm of your hand and roll into a ball.
5. Make an indentation in the center with your finger.
6. Place your choice of desired filling in the indentation.
7. In small bowls, make up a combination of fillings that you enjoy.
8. Dip fingers into water and pack rice firmly around filling to make a small ball.
9. Repeat with remaining rice and your choice of filling.
10. Sprinkle each popper with toasted sesame seeds and a dot of wasabi paste and place on a platter.
11. Cover with plastic wrap and keep at room temperature until ready to serve.