To start the salad, cook the noodles according to packet instructions and set aside.
Cut the Chinese leaf into thin strips and place into a large salad bowl. Cut the tomatoes into wedges and add to the bowl.
Cut the cucumber in half and remove the seeds with a teaspoon. Cut into 8cm long strips and mix into the salad.
De-seed the red pepper and finely dice. Slice the spring onions, add to the bowl with the pepper and cooked noodles, mixing to combine.
For the dressing, place the sugar in a bowl. Add the lime juice and stir until the sugar dissolves, then add the soy sauce.
Fry the strips of beef in a hot pan with the oil for a few seconds until warmed through then drain on kitchen paper.
Dress the salad with the dressing and divide into bowls. Lay the strips of beef on top and garnish with torn mint and coriander. Serve immediately.