Pumpkin curry with chickpeas

Name: Pumpkin curry with chickpeas
Prep time: 20 min
Cook time: 20 min
Total time: 40 min
Cuisine: Thai
Ingredients: 1 tbsp sunflower oil; 3 tbsp Thai yellow curry paste or vegetarian alternative; 2 onions finely chopped; 3 large stalks lemongrass bashed with the back of a knife; 6 cardamom pods; 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 limes; large handful mint leaves; naan bread to serve