Step 2

Stir together the lime zest, lime juice, fish sauce (or soy sauce) and sugar. Toss into the noodles with the sliced red onion and lettuce.

Step 3

Pork variation: heat a little oil in a non-stick pan and stir-fry the minced pork with the grated ginger and cayenne for about 10 minutes until browned. Mix into the noodles and serve warm.

Step 4

Steak variation: tip the sesame seeds onto a plate. Rub each steak with a little oil and press into the sesame seeds to coat. Fry in a hot pan for about 5 minutes for medium rare, turning halfway. Rest for 5 minutes, then slice thinly. Toss the shredded chilli and mint into the noodles and top with the steak slices.