Remove the steak from the refrigerator 1 or 2 hours before cooking and wipe it dry.
Separate the leaves of the lettuce, wash them and wipe dry with kitchen towel. Put them in a large serving dish.
Thinly slice the radishes and spring onions, then add to the lettuce.
Cut the cucumber in half lengthwise, scrape the seeds out, then slice thinly and add to the salad.
Rub the steak with a little oil, season with salt, then grill it on a barbecue or in a griddle pan for 2-3 minutes on each side (or longer for well-done). Rest for 5 minutes on a warm plate.
The dressing: mix the chilli, ginger, sugar, oil, soy sauce and lime juice.
Thinly slice the steak across the grain and place the strips on top of the salad. Drizzle with the dressing and scatter over the coriander leaves.