Place the corn cobs in a soup kettle. Add the milk and chicken stock. Bring to a boil and simmer for 1 hour.

Remove the cobs and add the corn kernels, salt, and sugar. Continue to simmer as the corn cooks. With a small spoon, scrape away the pulp from the cobs and add it to the chowder.

Chop the scallions, including most of the green tops, and briefly sauté them in 4 tablespoons of the butter.

Set aside. In a small bowl, blend the remaining 1 tablespoon butter with the flour. Whisk the flour mixture into the chowder. Season with pepper to taste and the cayenne and cook for another 15 minutes.

Fold in the scallion mixture. Taste for seasoning and serve in heated soup plates.