Cut pork fillet into thin, bite-sized slices. Prepare your marinade and refrigerate pork in marinade for 1 hour.
While marinating, thaw peas in a colander.
Prep all vegetables: peel carrot and cut into small cubes; peel and roughly dice onion; clean bell peppers and cut into small cubes; peel ginger and finely mince; remove seeds from chilli pepper and finely mince; mince garlic; clean spring onions, cut into rings, and separate white and green parts.
Prepare your sauce.
Heat wok to medium-high. Remove pork from marinade and working in batches, fry for 1-2 min per side over high heat until cooked through (internal temperature 63°C/145°F). Set aside.
In the same wok at medium-high heat, fry carrot, onion, garlic, chilli, and ginger for 2 min, stirring constantly. Add bell peppers and white parts of spring onions, stir-fry for 2-3 min.
Pour sauce into wok. Add lemongrass and bring to a boil briefly, then reduce heat to medium.
Return cooked pork and green parts of spring onions to wok. Cover with lid and simmer for 1-2 min.
Add bean sprouts and simmer uncovered for 1-2 min.
Gently fold in pineapple pieces and peas, simmer for 1 min until heated through. Season with chilli sauce and ginger powder to taste.