Slice the kernels from each corn cob and place in a bowl. Set aside.
Break each corn cob in half and place in a large dutch oven or stock pot. Cover the cobs with 2 quarts of cold water. Bring the water to a boil and turn the heat to low. Simmer, uncovered, for 40 minutes.
While the corn cobs are simmering, heat the olive oil in a large pot over medium low heat. Add the onions and cook until translucent, approximately 2 minutes, then add the garlic, salt and reserved corn. Cook for several minutes until the corn is soft, stirring frequently, and then remove from the heat and cover.
Once the corn cobs have finished simmering, strain the liquid and add 2 cups of it to the corn mixture along with 2 cups of stock. If the corn stock has reduced to less than 2 cups, simply add more stock or plain water. Simmer the ingredients together over medium heat for an additional 15 minutes, covered.
Ladle the soup into a blender and puree in batches. Press the soup through a food mill or fine mesh strainer. Season with salt and pepper to taste. If a thinner consistency is desired, add additional stock (use the corn stock if there’s any leftover).
If using, garnish with creme fraiche and chives before serving.