1. Melt the butter in a heavy based saucepan and sauté the onion until soft but not coloured. Mix in the rice, thoroughly coating with the butter and onion followed by a ladle of hot stock. Gently stir until the stock has been thoroughly absorbed then repeat with another ladleful.
2. Set the timer to 10 minutes and continue to add the hot stock, ladle-by-ladle ensuring it has been thoroughly absorbed before adding the next. When the timer sounds add the wild asparagus and set the timer for a further 5 minutes. At this point you need to be attentive. The rice will need about 16 minutes cooking time, but may not absorb all of the stock, so, using a teaspoon, test a little - the risotto should have a slight 'bite' (al denté) whilst being creamy and not too dry.
3.Gently stir in the butter and parmesan cheese. Season to taste and serve immediately on warmed plates.