Peel and finely slice the onions. Coarsely grate the courgette.
Put a large pan over a medium heat for 2 mins. Add 2 tbsp oil, the onions and courgette. Season with a good pinch of salt and pepper. Cook for 10 mins, stirring now and then, till the veg are soft and lightly browned.
While the veg fry, halve, quarter or thickly slice the mushrooms, depending on how large they are.
Crumble the stock cubes into a large pan or bowl. Stir in 2 ltrs boiling water till the stock cubes dissolve. Set aside.
Add the mushrooms to the pan. Cook and stir for 2 mins till they're juicy. Stir in the rice. Cook and stir for 2 mins.
Add a ladleful of hot stock to the rice. Keep the heat set to medium-low and cook till the rice has absorbed the stock. Stir often, but not constantly - every few mins should do. Then keeping adding the stock and stirring till all the stock has been used up and the rice is soft and creamy
While the risotto cooks, roughly chop the herb leaves. When the risotto is ready, stir in the chopped herbs. Taste and add a little more salt or pepper if you think it need sit. Serve the risotto in warm bowls.