1.Preheat oven to 180°C/350°F.
2.Heat oil in a shallow large flameproof baking dish; cook onion and garlic, stirring, until onion softens. Add rice; stir to coat in onion mixture. Add wine; bring to the boil. Boil, uncovered, stirring, until liquid is absorbed. Stir in stock, the water, rind and juice; bring to the boil. Cover tightly, transfer to oven; cook for 25 minutes, stirring halfway through cooking time.
3.Meanwhile, shell and devein prawns, leaving tails intact.
4.Uncover risotto, return to oven; cook for 15 minutes. Stir in prawns, asparagus and broad beans, return to oven; cook, uncovered, for 10 minutes or until prawns change colour and rice is tender.
5.Serve bowls of risotto topped with mint.
You will need about 500g (1 pound) fresh broad beans in the pod to get the required amount of shelled beans. Not suitable to freezeNote