Heat a wok and add about 1 tbsp of the groundnut oil. Stir fry the red onion for a few minutes until soft and slightly coloured. Add the chopped prawns, garlic and a pinch each of salt and sugar. Stir fry until the prawns are pink and just cooked through. Remove from the heat and transfer the contents of the wok to a large bowl.
To the bowl, add the spring onion, carrot, sugar snap peas, beansprouts and herbs. Season with a little more salt, sugar and a sprinkling of white pepper.
Place the noodles in a glass bowl. Pour over boiling water, stir and leave to stand for 5 minutes. Then, drain well and snip into short pieces with kitchen scissors.
Add the noodles to the prawn mixture and mix well. Taste for seasoning and adjust if necessary – the mixture should be quite well seasoned.
To make the spring rolls:
Fill a deep baking tray (or something similar) with hot water from the tap. Fold a clean tea towel in half and lay it on a worktop. Place a spring roll wrapper in the water and let it soften for about 15-20 seconds until pliable. Transfer to the tea towel and place 2 tablespoons of the mixture in the bottom half of the wapper. Starting with the edge nearest to you, roll it up, tucking in the sides as you go. Repeat this process until all the filling is used up.
If you are having these as ‘fresh’ spring rolls, they are now ready to serve with the lettuce leaves and your choice of dipping sauce.
If you are serving them as ‘crispy’ spring rolls, heat enough oil in a wok or large pan to deep fry. Once the oil is really hot, cook the spring rolls two at a time until golden brown on all sides (you will have to flip them over during cooking).
If they stick to the pan or each other during cooking, leave them until really crispy before trying to separate them or they will just tear. Drain on kitchen paper and then serve with the lettuce and dipping sauce. You can deep fry them ahead of time and reheat in the oven – they crisp up again really well.