Warm the stock, then add the saffron and leave it to infuse for 10 minutes. Meanwhile, heat the oil in a large frying pan and fry the carrots, garlic and leeks over a low heat for 10 minutes, until they are softened but not coloured.
Bring the stock to simmering point. Meanwhile, add the rice to the vegetables and stir for 1 minute or until the grains are glossy.
Keep the stock simmering and add a ladleful to the rice. Stir continuously until it has been absorbed. Continue adding the stock a ladleful at a time, and stirring, for 15 minutes.
Add the asparagus, beans and peas to the rice and continue stirring and adding stock for a further 15-20 minutes until the rice and vegetables are tender.
Remove the pan from the heat and stir in the herbs and Parmesan, then cover and leave to rest for 5 minutes. Season to taste and serve.