Tip the couscous into a heatproof bowl. Add a pinch of China 5 spice and some salt. Mix together. Pour over just enough water to cover the grains by 1 cm. Cover with cling film or a plate and leave to steam cook.
Halve the cucumber lengthways and scoop out the seeds with a teaspoon. Discard the seeds. Chop the cucumber into small cubes. Finely slice the spring onions. Tear the lettuce.
Halve the plums and scoop out the stone. Roughly chop them. Zest and juice the lime.
Heat a frying pan. When hot, drizzle in 1 tbsp olive oil. Add the chicken breast fillets and cook for 8 mins till golden and cooked through. Remove from the pan and set on a plate.
Keep the pan on the heat. Add the plums and cook for 2 mins. Pour in 200ml boiling water and bring to a bubble. Reduce the heat and leave to simmer for 5 mins, till the plums are soft.
Pour in 2 tbsp honey and the lime juice. Sprinkle in 1 tsp China 5 spice. Stir. Add the chicken fillets with any resting juices back to the pan. Cover with the lid and cook for 5 mins.
Lay the torn lettuce on a platter. Fold half the spring onions and all the cucumber into the steamed couscous. Add the lime zest and 1 tbsp olive oil and toss to combine.
Scatter the couscous salad over the lettuce. Spoon over the chicken and the plum sauce. Garnish with fresh basil leaves and the remaining spring onions.