Remove any string and trim the neck skin from the poussin.
Cut off the ends of the legs.
Cut through one side of the backbone with a large knife.
Cut through the other side of the backbone and discard it.
Press the breast down hard to break the breastbone and flatten the bird.
Make incisions in the skin flap, thread the legs through, and tuck the wings under.
Grind cardamom seeds, coriander, and cumin in a mortar.
Add turmeric and finely chopped ginger to the spice mix.
Add garlic and pound into a paste, then stir in oil, salt, and pepper.
Rub the poussin with marinade and chill for 30 minutes.
Preheat the oven to 180°C and griddle the poussin for 5-10 minutes per side.
Roast in the oven for 15-20 minutes until the juices run clear.
Combine tomatoes, vinegar, water, and sugar in a heavy-bottomed pan.
Add garlic, chilli, and mustard then simmer for 1 hour until thick.
Serve the poussin with lime juice, jam, and naan bread.