Heat the butter or oil in a lidded pan over a medium heat and gently fry the onion with a large pinch of salt, stirring occasionally for 10 mins until soft and golden.
Stir in the whole spices and the bay and cook for 2 mins more. Add the ground coriander and turmeric, and cook for 1 min more. Gently stir in the drained rice to coat it in the onion mixture, then pour over the water and stir well.
Cover the pan with a lid and bring to the boil, once boiling turn the heat down and simmer gently for 8 minutes.
Add the frozen peas, stir into the rice, replace the lid and continue cooking for another 3 minutes.