Shell and devein the prawns, leave the tails on if desired. Cut the asparagus into 3cm lengths.
Combine the wine and stock in a saucepan then heat until almost boiling, then put aside.
Melt butter in a large saucepan and saute the onion and garlic until soft. Add the rice and stir to coat with the butter mixture. Continue to stir while adding 1 cup of the stock until fully absorbed then add another cup. Continue to add the stock one cup at a time until all added and absorbed. This normally takes about 40 minutes.
Add the prawns and asparagus, then gently fold until prawns change colour and asparagus starts to soften. Serve straight away with grated parmesan and cracked pepper.