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.
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.
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.