Preheat the oven to 220C/gas 7/fan 200C.
Pour the oil into a large roasting tray or ovenproof dish and put in the oven for a couple of minutes to heat through.
Add all the vegetables to the tray except the green beans stirring well to coat them in the hot oil.
Now season with salt and pepper and return to the oven for 12 minutes until beginning to brown.
While the vegetables are roasting stir together the stock, curry paste, chilli, saffron and mustard seeds.
Now mix the rice and green beans with the vegetables in the oven tin.
Then add the stock mixture and stir well.
Lower the oven to 190C/gas 5/fan 190C.
Cover the dish tightly with foil and bake until the rice is tender, and the liquid has been absorbed.
Stir in the lemon juice and check the seasoning then scatter over the coriander and cashews.