How do I prevent clumps when using cornstarch to thicken a soup?
I've made cold cherry soup a few times from a recipe that calls for thickening it with a little cornstarch, but I always end up with some small clumps of what I presume are the starch in the finished soup. I don't cook with cornstarch much, so I don't know where in the process I'm going wrong.
The recipe calls for cooking the cherries in water with spices for a while and then combining cornstarch (2 tablespoons, in this recipe) with a like amount of the hot soup mix, stirring rapidly to combine, and then stirring that back into the pot of soup. (While trying to diagnose my problem I've come across other recipes that call for combining the cornstarch with cold water. That's not what I did. I haven't tried that.) When I combined the liquid with the cornstarch I couldn't get all the lumps out, so I added some more soup from the pot until I got something that seemed smooth. I then stirred that back into the pot and, again, everything seemed smooth, though it's easier for clumps to hide among cherries than in a bowl of liquid. I then simmered that for a while longer before cooling it, letting it sit out until it was cool enough to safely put in the fridge.
Where did I go wrong with the cornstarch? What do I need to change the next time I make this? This has happened to me a few times, but I only pit that many fresh cherries about once a year, so I always manage to forget by the next time I'm doing this. This time I remembered to ask the question. :-)
I have considered just leaving it out, preferring a thinner soup to lumps, but learning how to properly use cornstarch will probably help me with other cooking in the future, too.