Allow dried scallops to soak in a bowl of cold water for 2½ hours. Then tear them into thin shreds, blot dry with a paper towel, and divide into two piles.
Heat 1 tablespoon oil in a wok or a large deep frying pan over medium heat, and fry half of shredded scallops for about 3 minutes until golden-brown and crisp. Pour scallop shreds and hot oil through a mesh strainer and set aside.
Steam remaining scallops with the cooking wine for 15 minutes either in a parchment-lined vegetable steamer or in a bowl on a steamer stand in a covered wok or pan. It’s important that the liquid not come into direct contact with the scallop shreds.
Cook rice in water or chicken broth in a rice cooker or covered saucepan. The liquid should only barely cover the rice so that the resulting texture is dry, not wet. When done, spread out rice in a wide dish to cool down. When cool, using a large flat spoon, gently fold the egg yolk into the rice, until it evenly covers the rice and has a uniform yellow color.
Heat 1 tablespoon peanut oil in a wok or large pan over medium heat. Gently stir fry the egg whites for about a minute until they are fluffy, like soft scrambled eggs without the yolk. Remove from pan and set aside.
With leftover oil in wok on high heat, spread rice evenly around pan, then push rice to the sides of the pan, leaving a space in the center. Put steamed scallop shreds in the center, followed by coins of choy sum, then mix the three ingredients together. Sprinkle with salt. Cook about 5 minutes until the grains of rice separate. Gently mix in egg whites and scallions. Finish with ground white pepper and fish sauce, and top with fried scallop shreds.