Curried Split Pea Soup

Melt the butter in a large pot. Add onion and leek and cook over low heat until softened, about 10 minutes. Add carrot, celery, garlic and bay leaves. Cover and simmer 30 minutes until vegetables are tender, stirring frequently. Add the curry powder, coriander, cardamom and rosemary. Cook, uncovered, stirring continuously until the spices have dissolved into a paste. Stir in the tomatoes, breaking them up with a spoon. Raise the heat and bring soup to a boil. Add the broth and reduce heat to a simmer. Add the peas and ham bone or hock. Add some water if needed to cover ham bone. Reduce the heat to a very low simmer and cook, covered, 4 hours, stirring and turning the ham bone occasionally. Remove the ham bone and blend soup in a food processor. Return soup to the pan and heat to a simmer. Thin soup with additional broth or water if necessary. Adjust seasonings. Garnish with a dollop of yogurt if desired.