Fry the onion in the vegetable or coconut oil until soft and translucent. Add the garlic, ginger and curry paste and fry for two minutes. Add the sweet potatoes, water and stock cube. Cover, lower the heat and boil for 20 minutes or until sweet potatoes are cooked through and soft. Remove from the heat and liquidise with a stick blender or in a liquidiser. Check consistency, if it’s too thick at this stage, add some more water. Stir in the coconut milk and set aside.
Heat vegetable oil in a saucepan (you need at least 2cm oil) and drop the poppadom strips into the hot oil a few at a time. These will cook pretty much instantly – in 2-3 seconds (I kid you not). Lift and drain on kitchen paper to get rid of excess oil. As they cool they will crisp up beautifully.
Heat the soup through and stir in the juice of one lime. Taste and add salt (if needed) and freshly ground black pepper. Serve with the poppadom ribbons, lime wedges for guests to add an extra bit of zing to their soup (it really transforms it), coconut shavings and coriander.