First make the raita. Grate the cucumber coarsely without peeling it. Spread it out in a colander and sprinkle with the salt. Leave for 30-60 minutes. Squeeze out excess moisture then dry on kitchen paper. Mix with the yoghurt and set aside.
Heat the oil in a large saucepan and cook the onion and garlic gently for a couple of minutes. Add the spices and continue cooking until the onion is tender.
Stir in the rice and cook for a minute. Add the water, salt and pepper and bring to the boil. If using fresh whole broad beans add now. Reduce to a simmer, cover tightly and cook for 10 minutes.
Add the shrimps and thawed broad beans if using. Stir then cover again and cook for 5-10 minutes until the rice is tender and all the liquid has been absorbed. If needed add a little more hot water as the rice cooks.
Stir in the coriander and adjust the seasoning. Serve with the raita.