Heat the oven to 190°C/Fan 170°C/Gas 5. Halve the courgettes lengthways. Use a teaspoon to scoop out the seeds. Pop the courgettes on a baking tray. Bake for 20 mins to soften slightly.
While the courgettes bake, tip the quinoa into a sieve. Rinse it under cold water for 1-2 mins. Tip the rinsed quinoa into a small pan. Add 150ml boiling water and a pinch of salt. Cover. Bring to the boil. Turn the heat right down and gently simmer for 15 mins till the water is absorbed.
While the quinoa cooks, tip the cashews into a dry frying pan. Toast for 2-3 mins, shaking the pan occasionally, till they're browned. Tip out onto a chopping board. Roughly chop them. Scoop the chopped nuts into a bowl.
Trim the roots off the spring onions. Finely slice them. Add to the cashews. Finely grate in the lemon zest. Tear in the basil leaves. Finely chop the mint leaves and add them too.
Add half the quinoa to the bowl once it has cooked, draining off any excess water. Season well with salt and pepper and squeeze in a little juice from the zested lemon. Stir together.
Take the courgettes out of the oven. Spoon in the quinoa stuffing. Return to the oven and bake for 20 mins till tender.
While the stuffed courgettes bake, roughly chop the tomatoes. Tumble them into a bowl with the lamb's lettuce and the remaining quinoa.
Whisk 1 tbsp balsamic vinegar with ½ tbsp olive oil, a squeeze of lemon juice and some salt and pepper. Toss with the salad. Serve the stuffed courgettes with the salad and any remaining stuffing on the side.