Put stock, shallots, ginger, star anise, peppercorns, cinnamon, coriander seeds and chillies in slow cooker together and cook on low for about 5 hours; or a large pot over a medium heat, bring to the boil, reduce heat and simmer, partially covered, for about 45 minutes. If using a pot to make the stock I add some stock to the slow cooker and turn it on low while the stock simmers in the pot so that I am not adding the stock to a cold slow cooker when getting to that step.