In a large heavy-bottomed pot, melt the butter. Add the diced onion and cook until soft and translucent, about 15 minutes. Do not brown. Once the onion is soft, add the corn kernels and stir to combine. Cook for 2-3 minutes. Cover with water and bring to a boil. Once boiling, reduce heat to a simmer and cook for 5 minutes. Let soup cool slightly.
Puree soup in a blender in batches. Be careful when blending hot soup and always make sure there is an air vent to allow steam to escape. Pour pureed soup through a mesh strainer to remove any tough skins and to make it as smooth as possible. Reheat soup before serving, making sure to season with sea salt to taste. Ladle soup into individual bowls and garnish with a dollop of creme fraiche, a sprinkle of savory, and a drizzle of extra virgin olive oil.