Melt the butter in a large saucepan over medium heat. Add the onion and cook until translucent, about 5 minutes.
Add the potatoes, corn, milk, chicken broth and chicken thighs. Bring to a boil, skim off the foam, then reduce and simmer 20–30 minutes, until the potatoes are tender and the chicken is cooked through.
Transfer 2 cups of the soup to a blender; purée, then return it to the pot. Season with the cayenne, salt and pepper. Stir in the parsley, if using, or sprinkle it on top of individual bowls as a garnish.
Notes
Blend for body: Puréeing 2 cups and stirring it back gives a creamy chowder without much added cream.Use the corn liquid: It adds sweetness and corn flavour — don't drain it.Skim the foam: Skimming after it boils keeps the broth clean.Adjust the thickness: Add more broth if it gets too thick as it simmers.