Soak rice in cold water for at least 45 minutes or overnight. Drain rice and mix with salt.
Remove the stems from the mushrooms and chop the stems.
Mix chopped stems with pork, rice wine, sugar, soy sauce and corn starch.
Score the backs of the mushrooms, cutting a petal design.
Fill the mushroom caps with the meat mixture.
Spread the salted rice on a plate and press the filled mushrooms caps into the rice to coat the meat.
Spread sesame oil on a heatproof dish and place the filled mushroom caps.
Steam for 30 minutes. Serve with dipping sauce of vinegar and soy sauce mixed together.