First, make the sauce. In a small jug, mix the soy sauce, oyster sauce, vinegar, brown sugar, sesame oil, and water.
Heat the oil in a large frying pan to medium heat. Add the onion and chorizo, cooking for 5-8 minutes until golden brown. Add chilli and stir. Push it to the outside and add the eggs, mixing it to form a small omelette. Remove from the pan.
Add the prawns and cook until pink and juicy. Add the chorizo back in with the noodles, sauce, and finally, bean sprouts, combining everything until hot.
Serve with a squeeze of lime or lemon.