Separate the cabbage leaves, rinse them well and drain them thoroughly. Pat them dry with a kitchen towel or paper towels.
Working with one leaf at a time, lay it flat on a cutting board and make a V-cut to separate the white ribs from the leafy parts. Repeat with the remaining leaves. Slice the ribs into 1-inch pieces at a 45-degree angle. Cut the leafy parts of the leaves into similar-sized pieces. Keep the ribs and leaves in separate bowls.
In a small bowl, mix 1 tablespoon of the vinegar with the soy sauce, sugar, starch and water. Stir until the sugar has dissolved.
Heat the oil in a wok over low heat. Add the Sichuan pepper and chilies and fry for about 1 minute, until the chilies turn dark brown. Remove the chilies and peppercorns, leaving the infused oil in the wok; save the chilies for garnish.
Turn the heat up to medium-high. Add the garlic to the infused oil and stir-fry until it is golden and fragrant. Add the cabbage ribs and cook them for 1½ minutes, then, add the ruffly leaves and stir-fry everything for another 30–45 seconds, just until wilted.
Give the sauce a final stir and pour it into the wok. Toss everything together and stir-fry the mixture for 1 more minute, until the sauce turns glossy. Add the salt and mix well, then turn off the heat.
Drizzle in the remaining 1 teaspoon vinegar, add the sesame oil and toss everything quickly. Serve immediately.
