Cut the kernels from the cob, and set aside in a bowl. Cut two of the onions in half, and chop the last one.
Add the cobs, onions halves, garlic, and salt to a medium pot. Add enough water to cover the cobs completely. Bring to a boil over high heat. Reduce to low heat, and simmer 20 minutes. Let cool, if you have the time, but not a deal breaker if you're in a rush.
Pour the broth through a sieve, and discard the cobs, onions, and garlic.
Add a swirl of oil to a deep skillet or medium pot. Heat over medium flame until shimmering. Add the corn and chopped onion to the pot. Sauté until corn brightens, and onion gets slightly tender.
Add the broth, and increase heat to high, Bring to a boil. Reduce heat to low, and simmer until corn is tender, but still has some bite to it.
Use an immersion blender to puree the soup into a chunk chowder-like consistency. Alternately, add half the soup to a blender, puree roughly, then stir back into the pot.
Ladle the soup into bowls. Garnish with a swirl of regular cream or cashew cream, lemon zest, and fresh lemon thyme leaves, and serve immediately.