Mix the yogurt with the cornstarch and set to one side. Cut each of the chicken breasts into 3 or 4 chunky pieces.
Lightly crush the cardamom pods so that the green husks split open, then remove the little brownish-black seeds from inside. Grind these into a fine powder with a pestle and mortar.
Heat the oil and butter in a flameproof casserole dish, add the chicken and cook over a medium heat until lightly browned all over. Add the turmeric, cinnamon, coriander and ground cardamom seeds and cook for a further minute.
Remove the pan from the heat and stir in the broth, grated ginger, lemon juice and the yogurt mixture. Return the pan to the heat, bring to a simmer and leave to cook gently for 15 minutes until the chicken is tender. (You can now set the dish aside until later if you wish).
Mix the cream with the ground almonds, stir into the chicken and simmer for 2-3 minutes. Season to taste and serve, garnished with sprigs of cilantro.