Season the prawns with soy sauce and white pepper and set it aside. Mix all the stir fry sauce in a small bowl and whisk until sugar dissolved.
Heat the wok/pan into low-medium heat. Sautee the raw cashew nuts with a teaspoon of oil until crispy golden brown. Remove from the pan and set it aside.
In the remaining wok/pan drizzle 1 tablespoon of oil and stir fry the marinated prawns over medium-high heat for 1-2 minutes. Once the prawns are charred and 80% cooked, removed from heat and set it aside.
Drizzle 2 tablespoon of oil and stir fry onion and dry chillies over medium high heat for a few seconds. Follow with the chopped garlic, ginger, and Sichuan peppercorns. Toss for a few seconds until fragrant then add the bell peppers.
Place the cooked prawns back in the wok and pour the sauce in.
Once the sauce is thick and glossy, turn off the heat and stir in toasted cashew nuts and spring onions.
Remove from heat and transfer to serving plate. Serve immediately with plain rice or noodles.