BRING THE BROTH TO A SIMMER in a pot and add the ham, bean curd and mushrooms. Let it simmer 5 minutes. Heat the oil in a wok to very hot (about 380F).
Test the oil by dropping a small piece of Rice Crust into it. It should float immediately.
Slip the whole Rice Crust into the oil. As it begins to puff up like popcorn, break it up into large chunks with long chopsticks.
Turn it to brown on all sides (about 1 minute). Remove the rice and drain it. At the table, add the rice to the serving bowl of soup.
It will sizzle as the steam rises and provide quite a show. Add the scallions and sesame oil just before serving. (The oil used for deep-frying can be cooled, strained through a fine sieve and stored in a jar for future use.)
FOR RICE CRUST:
Prepare rice as you normally would, but cook it in a wide, heavy pot at least 15 minutes after the rice is soft so that a crust forms on the bottom of the pot.
Spoon off the top layer of loose rice and set aside for Fried Rice or freeze it for future use. If left to stand overnight at room temperature, the crust will be easier to remove from the pot.
To use the rice right away, keep the pot on low heat and dribble peanut oil around the edge. Heat for a few minutes, then loosen the crust with a spatula. It should come out in one whole piece. Invert the crust onto a plate. It can now be frozen for future use or used while still hot.