Step 1Rinse the rice thoroughly in cold water, and then soak for 3 hours in hot water, or overnight in cold water; drain and set aside.
Step 2Meanwhile, soak the dried shrimp and the shiitake mushrooms in separate bowls of hot water for about 30 minutes to reconstitute. After soaking, drain, squeeze dry and finely chop them separately. Finely chop the ham; set aside.
Step 3Peel the water chestnuts if you are using fresh ones, then chop them finely by hand.
Step 4In a medium bowl, combine the water chestnuts, ground pork, ginger, wine, egg and potato flour mixture. Season with three-fourths teaspoon salt and one-half teaspoon pepper, or to taste. On a plate or in a shallow baking dish, combine the ham and shiitake with the drained rice. Lightly grease a heatproof plate with peanut oil (choose one that will fit comfortably inside a steamer).
Step 5Shape the meat mixture into walnut-sized balls and roll in the rice mixture to coat generously. Lay the meatballs in one layer on the oiled plate; you might need to steam them in two batches, depending on the size of your steamer.
Step 6Steam, tightly covered, over high heat until cooked through, about 10 minutes; break one in half to check that it is cooked. Serve directly on the plate, with a scattering of green onion and sesame oil.