For the dressing: finely chop the chilli (discarding the seeds) and mix everything together well. Season with salt and pepper.
Wash the lettuce and bean sprouts, dry them, and cut the larger leaves into smaller pieces.
Halve and stone the plums, then cut them into thin slices; cut the radishes into quarters.
Cut the cucumber lengthwise, remove the seeds with a teaspoon, and slice into half-moons. Roughly chop the mint and slice the spring onions diagonally.
Place all the ingredients—except the nuts—in a bowl and pour the dressing over them.
Roughly chop the nuts and scatter them over the salad before serving.