Bring the stock to a boil in a large pot, then reduce the heat, add the asparagus, carrots, peas and fava beans and simmer for 4-5 minutes until the vegetables are tender. Remove the vegetables with a slotted spoon and set aside. Keep the stock simmering over a gentle heat.
Meanwhile, heat the oil in a large, heavy-based frying pan and add the leeks. Stir-fry for 2 minutes until they are bright green, then stir in the rice.
Add 2-3 tablespoons of the hot stock and cook gently, stirring until the liquid is absorbed. Continue adding the stock, only a ladleful at a time, making sure each is almost completely absorbed before adding the next, and stirring frequently to produce a creamy texture.
Once all the stock has been absorbed and the rice is tender (this will take about 20 minutes), stir in the pesto and season to taste. Gently stir in the asparagus, carrots, peas and beans and cook for a few more minutes until the vegetables are heated through. Serve in heated soup plates and scatter the pine nuts over the top.
Variation: When fresh peas and fava beans are not in season, use frozen peas and fava beans.
Cook's tips: There are many varieties of pre-made pesto on the market. Those that contain Parmesan cheese are not suitable for strict vegetarians.
Each serving: 21 g protein, 16 g fat of which 2.5 g saturates, 78 g carbohydrate, 12 g fibre, 392 Calories