To make the sauce place a medium saucepan over a low heat. Add shallots, ginger and garlic sauté for around 5 minutes or until translucent. Add the turmeric and fenugreek and continue to cook for a further 5 minutes. Add the pumpkin, coconut milk and cream with the stock. Bring to the boil then simmer for about 10 minutes uncovered until the pumpkin is soft. Add fish sauce, blend until smooth and pass through a sieve to be sure. Season with salt and pepper to taste.