1 medium Yukon Gold potato, peeled and cut into 1/2-inch dice
1/2 cup dry white wine
1 thyme sprig
1/2 cup heavy cream
Chive flowers, pulled apart, for garnish
In a large pot, bring 12 cups of water to a boil. Add the corn, cover and cook over moderately high heat until barely tender, about 5 minutes. Using tongs, transfer the corn to a bowl to cool.
Cut the kernels from the cobs. Return the cobs to the pot, cover and simmer for 30 minutes. Discard the cobs and reserve the corn broth; you should have about 4 cups.
In another large pot, melt 2 tablespoons of the butter. Add the onions, cover and cook over moderate heat, stirring occasionally, until softened, about 8 minutes. Add the sugar and cook over moderate heat until the onions are caramelized, about 4 minutes.
Reserve 1 cup of the corn kernels. Add the remaining corn kernels and the potato to the onions in the pot. Add the wine and simmer over moderately high heat until almost evaporated, about 2 minutes. Add the corn broth, thyme sprig and cream, cover and simmer until the potatoes are tender, about 10 minutes.
Discard the thyme sprig. Working in batches, puree the soup in a blender. Return the soup to the pot and season with salt and pepper.
In a medium skillet, melt the remaining 1 tablespoon of butter. Add the reserved 1 cup of corn kernels, cover and cook over moderately high heat until richly browned, about 3 minutes. Season with salt. Ladle the soup into bowls, garnish with the sautéed corn and chive flowers and serve .