Just before cooking, husk the corn, pull off the silky threads, and cut out any blemishes with a pointed knife. Drop the corn into a large pot filled with boiling salted water. Cover the pot and let the water return to a boil again, then turn off the heat and keep the pot covered. After about 5 minutes, remove enough ears for a first serving. You can keep the remaining corn warm in the water for another 10 minutes without its becoming tough. Serve with lots of butter and salt.