Pumpkin curry with chickpeas

Name: Pumpkin curry with chickpeas
Ingredients: 1 tbsp sunflower oil; 3 tbsp Thai yellow curry paste, or vegetarian alternative; 2 onion, finely chopped; 3 large stalks lemongrass, bashed with the back of a knife; 6 cardamom pod; 1 tbsp mustard seed; 1 piece pumpkin or a small squash (about 1kg); 250ml vegetable stock; 400ml can reduced-fat coconut milk; 400g can chickpea, drained and rinsed; 2 lime; large handful mint leaves; naan bread, to serve