1. Cut Napa cabbage into sixths, core and slice across each section into 2-inch (5 cm) wide sections; mix well with salt. Cover; set aside at room temperature for 1 day in warm weather or 2 in cooler weather (taste after 1 day to see if the cabbage has soured). Rinse lightly under cold running water; drain, squeezing out excess moisture. Set aside.

2. In a dry frying pan over medium heat, toast Szechuan peppercorns until fragrant and slightly darkened. Toast chilies until fragrant and slightly darker in color. Stir together cabbage, Szechuan peppercorns, chilies, ginger and garlic (if using), pressing with your hands to extract liquid from cabbage and to break up the chilies. Cover; refrigerate 1 day before serving.