Tip the couscous into a bowl. Add a pinch of salt and stir through. Pour in enough boiling water to cover the grains by 1cm. Cover with cling film or a plate and leave to soak while you prepare the rest of your salad.
Slice the base from your lettuce. Arrange the leaves on a large platter or individual plates.
Put a large frying pan over a high heat to warm up. Cut your cucumber in half. Slice again into short quarters if your frying pan isn't big enough for the cucumber halves.
Add the cucumber to the hot pan (no oil needed), skin-side down. Fry for 3-5 mins till the cucumber skin is lightly charred all over. Lift out of the pan and set aside on a board, sprinkled with a little salt.
Trim the roots off the spring onions and finely slice them. Put the frying pan back on the heat. Add them to the hot pan (again, no oil). Cook and stir till a tender and a little charred. Add to the board with the cucumber.
Finely shred the mint leaves. Fluff the couscous with a fork and drain off any water if you need to. Add the mint. Finely grate in the zest of the lemon then add a good squeeze of juice and 1 tbsp olive oil. Taste. Season with salt and pepper. Taste and add more seasoning or lemon juice if you think it needs it.
Halve the charred cucumber lengthways. Thinly slice into half moons. Toss them and the charred spring onion into the couscous. Scatter the couscous over the lettuce and serve.