Mix together the marinade with the meat; set aside while preparing the rest.
Mix the liquid ingredients, brown sugar and corn starch and set aside to use as the sauce for stir-frying. Heat up wok with vegetable oil until shimmering and hot, about 120° C.
Dip half of the meat into the oil and move around until half-cooked, around 2 minutes; remove with slotted spoon and drain from oil. Repeat for the other half.
Drain off all but 2 tbsp of oil in heated wok, throw in chiles, peppercorns, garlic, ginger and spring onion; stir-fry until fragrant, about 2 minutes; add peanuts and stir-fry for another 1-2 min.
Add chicken cubes, stir-fry for about 3 minutes, or until chicken is cooked.
Pour on reserved sauce and simmer until the dish thickens, about 3 minutes.
Garnish with ground Sichuan peppercorn; serve with rice.
