Bring water to boil. Lower heat slightly. Add split peas, bay leaf and turmeric and simmer covered until peas are tender, 40 -45 minutes. During this period, uncover occasionally and stir, adding a tablespoon or so of hot water to prevent the mixture sticking to the bottom of the pan. Add salt. Keep warm.
Meanwhile, heat oil in a skillet over medium low heat. Fry ginger and green chilli until ginger is lightly browned, 1-2 minutes. Add mustard paste and fry for another minute, stirring occasionally (you may need to keep the skillet partially covered for a few seconds if the spices start to splatter the cooking area). Add coconut and stir several times. Remove from heat.
Pour over the pea mixture and stir. Cover and let stand for 15 minutes to develop the flavours. Garnish with coriander.