Place the peas and stock into a pan, stir well and bring to the boil. Cover the pan with a lid and reduce the heat to a simmer. Simmer, stirring regularly, for 40-50 minutes, or until the peas are just tender, adding some water as necessary. When the peas have cooked, remove them from the heat and whisk to break them down to your desired consistency. Set aside to cool.
Heat the oil & butter in a pan over a medium heat add the onion and ginger. Fry for 4-5 minutes, or until golden brown then add the garlic and cook for another minute. Puree the tomatoes in a food processor, add them to the pan and mix them in. Add the remaining spices and the water to the pan and stir well. Simmer over a medium heat for 15-20 minutes, or until the oil from the sauce has risen to the surface of the sauce. When finished, puree the sauce in a food processor and add it to the cooked peas & stock mixture and stir well (adding more water if necessary to loosen the mixture). Bring the mixture to the boil and season to taste, with salt and black pepper and chopped cilantro/coriander just before serving. Serve on rice or alone as a soup.