1. Cover brisket with cold water and bring to the boil. Drain,discarding water. Rinse well and set aside. Combine all other brisket ingredients in a clean pot with 2½ litres cold water and bring to the boil. Add brisket,turn heat down to barely simmering and cook for about 4 hours,until fork-tender. Once cooked,remove brisket and refrigerate overnight. Save the stock to reuse.
2. When you're ready to eat,cut brisket into 5mm-thick slices. In a wok,heat the vegetable oil to 180°C and deep-fry in small batches for 2 minutes,turning over halfway,until dark and crispy around the edges. Drain on a paper towel.
3. Wipe the wok clean,then place over medium heat and add the peanut oil. When the oil is hot,add the ginger and garlic and stir-fry until fragrant,then add the brisket and the rest of the ingredients,saving some Sichuan pepper to serve. Cook until the sauce is thick and almost reduced to a glaze. To finish,transfer to a serving plate,drizzle with sesame oil and garnish with finely sliced spring onions,then serve with rice and steamed Asian greens.