Combine all marinade ingredients in a bowl and massage into chicken, cover and let stand while sauce is prepared.
Reserve half the cashews and place remaining cashews in a food processor. Process until finely ground.
Heat butter and oil in a large saucepan over medium heat until butter is melted. Add onion and bay leaf and slowly cook until onion is golden, about 15-20 minutes. Reduce heat if onion browns too quickly. Stir in garam marsala, paprika, cumin, cinnamon and salt, cook for a minute. Add chicken and marinade, cook for 5 minutes tossing in onion mixture.
Add processed cashews, passata and stock. Simmer for 20 minutes.
Stir in Bulla Cooking Cream and cook for a further 15 minutes.
Serve with rice and garnish with reserved cashews and coriander leaves.