Heat your oven to 180°C/Fan 160°C/Gas 4. Trim the tops and bottoms off the leeks. Halve them and rinse out any grit. Finely slice them. Peel and finely chop the onion. Dice the courgette into small cubes. Grate the zest from the lemon. Put the lemon to one side for later.
Warm ½ tbsp oil in a large pan. Add the diced chicken leg. Fry, stirring, over a medium heat for 5 mins, till the chicken is golden all over.
Add the leeks, onion and courgette to the pan. Season with a pinch of salt and pepper. Fry for 5 mins till the veg are soft and juicy. While the veg fry, pop the stock cube into a heatproof measuring jug. Pour in 1 ltr boiling water and stir to mix.
Stir the risotto rice into the pan along with the lemon zest and thyme sprigs. Pour in the stock. Gently cook and stir the rice and veg over a medium heat for 5 mins.
Spoon the risotto into an ovenproof dish. Cover with a lid or foil, scrunching the sides to seal them. Bake in the oven for 30 mins, till almost all the stock is absorbed, then take the lid or foil off. Cook for a further 5 mins to dry it out a little.
While the risotto cooks, squeeze the juice from ½ the lemon into a small bowl. Add ½ tbsp oil and some seasoning. Whisk with a fork to make a dressing. Toss the salad leaves with the dressing.
Finely grate the parmesan and stir most of it into the risotto with a squeeze of juice from the remaining lemon half. Fish out the thyme. Taste and adjust the seasoning. Serve the risotto in bowls topped with the remaining parmesan and the salad on the side.