Sweet potato and ginger soup

I tried making a ginger and sweet potato soup from a recipe I found in the Guardian a couple of weeks ago:
http://www.guardian.co.uk/lifeandstyle/2013/jan/26/10-best-ginger-recipes

This soup is weird, though as I tasted tiny sips, I also found it strangely addictive. That said, I didn't even get to adding the cream or maple syrup before deciding it tasted more like a pudding than a soup.

I turned it into something much more savoury by adding:

• 1 extra tablespoon light soy sauce (so 2 in total)
• 1 tablespoon fish sauce
• 3 teaspoons tamarind paste 
• 2 large squeezes chilli paste

The original recipe does include lime juice which I will add after the soup is heated and before serving, otherwise it will taste bitter. 

I think this soup could be transformed into something much better and plan to try it with these modifications:

• Chilli seems essential to this recipe; ginger is just not enough
• More ginger to add a warm kick rather than a back note
• Coriander seeds to compliment the ginger and add depth of flavour
• Swap 1 sweet potato for a savoury root vegetable to reduce sweetness: maybe this is the swede recipe I have been looking for?
  http://www.localgreens.org.uk/redeem-swede-contest-registration
• Squash, pumpkin or celeriac could be worth considering. I think parsnip will be too sweet. (I also secretly hate parsnip but daren't admit it to anyone.)
• Add red lentils to thicken the soup: this will add roughage and make it more filling. Lentils in soup like this will have a negatory effect on flavour.
• I think some freshly chopped mint leaves would boost this soup no end, but, lets face it, most of us are unlikely to add this.

Oh, and this is probably just me, but I hate smooth soup I make myself. Maybe because I never add cream. But I prefer to mash it with a potato masher, leaving in some small chunks of vegetables. I also hate washing up the food processor more than any other job in the kitchen. 

Photo to follow.