Cut corn from cobs, scraping cobs well to remove all milk. Set corn aside.
Combine 1/4 cup milk and cornstarch; set aside.
Combine remaining 3/4 cup milk and onion in a large saucepan; bring to a boil over medium heat. Cover, reduce heat, and simmer 5 minutes; remove and discard onion.
Add corn to hot milk, and bring to a boil. Reduce heat, and cook 5 minutes, stirring often.
Add cornstarch mixture, salt, and pepper; cook, stirring constantly, 3 minutes or until thickened and bubbly.