Remember the two-coloured sweet potato balls? This is what I did with the extra purple sweet potato. I also had yam (white flesh with purple flecks) lying around getting rather withered so I put that in as well.
Getting a handheld blender* some years ago was a great move because blended soups are one of the easiest things to make and can be made with just about any combination of vegetables and other ingredients that takes your fancy. Besides the sweet potato and yam, this soup also has garlic and onions. More often my blended soups are based around cauliflower and cabbage (vegetables low in salicylates so food-intolerance-friendly), sometimes also pumpkin and potatoes.
The basic method is to lightly fry the vegetables which have been chopped into small pieces so that they cook more quickly. Use garlic and onions/shallots/spring onions/leeks for flavour if so desired, and start frying these first before adding the vegetables. Fry till the onions are limp and the vegetables are gently cooked. The browning effect makes the soup more flavourful. Then add soup stock or water and simmer till the vegetables are very soft and can be easily blended.
I also like to pulverise leftover dishes to ‘remake’ them into a different form. For example, chicken macaroni makes a nice and creamy tasting blended soup! If you include vegetables like leeks, celery, cabbage, potatoes etc. and use wholemeal pasta in the chicken macaroni, you get a pretty nutritious dish. And for times when you have a poor appetite, it’s much easier to swallow a liquid meal than chew through a solid one.
Actually, the sweet potato taste seemed to be more suited to a sweet dish than savoury soup. I imagine one could easily omit the other savoury ingredients, use milk (dairy or other types) for the liquid and make a Chinese-style creamy dessert paste similar to almond, walnut, peanut and sesame pastes.
*N.B.: A jug blender is more of a hassle to use because it’s so big and heavy and harder to wash up, but much quicker and more powerful – I use the jug blender for grinding soya beans when making soya bean milk. However for small amounts of softer, more liquid foods, the handheld blender is more convenient.