Begin by melting the butter in a medium saucepan, then add the onion and let it cook over a gentle heat for 5-7 minutes or until the onion is soft and golden.
Meanwhile, place the baking dish in the oven to warm through. Now add the rice to the saucepan, stirring it around to get a good coating of butter (it will look like there's not nearly enough rice at this stage, but it swells up during the cooking), then add the white wine and vegetable stock. Next, add the chopped sage, half a teaspoon of salt and some freshly milled black pepper and bring it up to simmering point, then transfer the whole lot from the pan to the warmed dish. Stir once, then place it on the centre shelf of the oven (without covering) to cook for exactly 20 minutes – a timer is useful here.
Meanwhile, heat the oil in a small frying pan. Add the whole sage leaves, a few at a time, and cook for 30 seconds to a minute until crispy, then remove with a slotted spoon to a plate lined with kitchen paper.
After the 20 minutes are up, remove the risotto from the oven and gently stir in the broad beans, asparagus and spring onions along with the 2 tablespoons of Pecorino cheese, turning the rice grains over. Now put the timer on again and cook the risotto for a further 15 minutes, then remove the dish from the oven, stir in the chives and put a clean tea cloth over it while you invite everyone to sit down. Risottos won't wait, so serve presto pronto on warmed plates and finished with a couple of crispy fried sage leaves and the extra grated Pecorino.
Preheat the oven to gas mark 2, 300°F (150°C).