1. Place cobs in a large soup pot with just enough water to cover (about 2 quarts). Add bay leaf, halved onion, and thyme, and bring to a boil. Reduce heat, cover, and simmer 30 minutes. Strain through a fine sieve into a bowl (you should have 1 quart). Stock can be refrigerated 3 days or frozen up to 3 months.

2. Heat oil in a deep pot over medium heat. Add chopped onion and garlic, and saute until onion is translucent, about 5 minutes. Add corn kernels, and saute 2 minutes.

3. Add stock, and simmer until liquid is reduced by half. Add half-and-half, and return to a simmer. Puree half the liquid in a blender until partially or completely smooth. (To prevent spattering, remove cap from hole in lid, and cover lid with a dish towel). Return to pot, heat, and season with 1 teaspoon salt and 1/4 teaspoon pepper. Divide among 4 bowls, and garnish with scallion and more pepper.