I made the nicest soup ever this week.
You take the cold, gnawed remains of a roast duck, and boil it in water. Then simmer for an hour with a little bag of herbs and stuff. Add lots of black pepper but no salt.
Then, chop up a big onion and cook it in olive oil till soft and a bit burnt (assuming you answer the phone during this phase of cooking). Add a load of peeled, cubed sweet potatoes and cook them in the onions and oil for a minute or two. Then pour the duck stock over it.
You need to ensure that all the bones and bits of herbs are no longer in the stock.
I recommend using a sieve for that. Unless you want to play "bobbing for bones" in a kind of gruesome Halloween party game way.
Bring to the boil, then simmer for 20 minutes, until the sweet potato is cooked. It's cooked when you can poke a fork through it with little effort.
Then, add some chopped fresh red pepper and simmer a bit longer.
Once the red pepper is soft, turn off the heat and stick in your handheld blender gadget. If you don't have one, get one. They are superb for making soup.
Whizz it all up till there are no lumps. Taste, add salt and more pepper, and it's ready to go.
I added a dollop of fresh yoghurt to mine, Mr WithaY chose to adorn his bowl with grated cheese. Both options worked.