Cut off the ends of the pineapple, stand the pineapple on end, and shave off the skin with downward strokes of the cleaver.
Cut the pineapple into ¾-inch cubes.
Drain the marinade from the pork, blot it dry, and dust the cubes with the water chestnut-almond powder or cornstarch-flour mixture. Shake off any excess.
Heat the oil in a wok to 360 degrees (moderately hot). Fry the pork cubes a handful at a time for 3 minutes. (They are done when they feel springy instead of mushy.) Set them aside.
Empty the wok of the oil (or do these next steps in a large saucepan). Heat the Sweet-and-Sour Sauce ingredients (except for the cornstarch dissolved in broth) over a moderate flame with the pineapple.
When it comes to a boil, stir in the dissolved cornstarch, the sesame oil, and the fried pork cubes to heat them through.
Sweet-and-Sour Pork—the tart fruit balances the richness of the pork.