Melt half of the butter in a large, deep-frying pan (or stockpot) over medium heat. Add the onion and cook without browning for 2 minutes or until soft. Add the asparagus and thyme. Cook, stirring, for a few minutes, then season with sea salt to taste.
Stir in the rice and after 2 minutes, pour in the wine. Cook, stirring, until all the liquid has been absorbed.
Add a ladleful of the hot stock, stirring constantly. When the stock has been absorbed, stir in another ladleful. Continue to add ladleful’s of stock, stirring and allowing each ladleful to be absorbed before adding the next until the rice is ‘al dente’ (approximately 15 minutes).
Remove the frying pan (or stockpot) from the heat. Stir in the remaining butter and Parmigiano Reggiano. Serve the risotto of asparagus with grated Parmigiano Reggiano on top – buon appetito.