In a large stockpot (8 quart minimum) on medium heat, melt the butter, add the onions, and cook until the onions are translucent (about 15 minutes).
Add the flour, salt, and turmeric; stir in thoroughly, and then add the chicken stock, potatoes, and chipotle chili.
Bring the soup to a boil and simmer uncovered for 15 minutes or until the potatoes are tender.
Add the corn, half-and-half, and cheddar cheese; simmer for 10 more minutes or until the cheese melted.
Serve hot and garnish with parsley or crumbled bacon if desired.