Shuck the corn, remove the silk, and cut off the stem end so the cob has a flat surface. Then stand each ear up on a cutting board and scrape off the kernels with a chef’s knife. Transfer the kernels to a bowl as you work.
Put the corncobs and 4 cups water in a large pot over medium-high heat. Sprinkle with salt and pepper. Bring to a boil, then lower the heat so the water bubbles gently. Cover and cook, checking to make sure the cobs are always covered with water, until the liquid is quite cloudy, about 30 minutes. Discard the corncobs and transfer 3 cups of the broth to a medium bowl or saucepan. (Save the rest if you like; no need to wipe out the pot.)
Return the pot to medium-high heat and add the butter. When it melts and foams, add the white parts of the scallions and the sugar and cook, stirring occasionally, until soft, about 1 minute. Lower the heat to medium and stir in the flour. Cook, stirring constantly with a wooden spoon, until the mixture starts to turn golden and the flour no longer smells raw, just a couple of minutes. Then add the cheese and stir until it just starts to melt, less than a minute.
Add the reserved corncob broth and milk and raise the heat to medium-high. Stir or whisk constantly until the flour is dissolved and the soup starts to thicken, about 2 minutes. Add the corn kernels and bring to a boil, then lower the heat so the soup bubbles gently. Cook, stirring occasionally, until the corn is tender and the soup has thickened, 10 to 15 minutes. Add a little more milk if you like a thinner soup. Taste, adjust the seasoning, garnish with the scallion greens, and serve.
|6 ears fresh corn||1/2 teaspoon sugar|
|Salt and freshly ground black pepper||1/4 cup all-purpose flour|
|4 tablespoons butter||1 cup grated cheddar cheese|
|2 scallions, white and green parts separated and chopped||3 cups whole milk, or more as needed|