Melt butter in a medium saucepan over low heat. Add salt, garlic and onions and sweat until translucent.
Remove corn kernels from cobs. Place cobs in a large pot, fill with water to cover cobs and simmer for about 40 minutes.
Add corn kernels to onion and garlic mixture and cook for about 5 minutes on low heat. Add salt to taste.
Strain corn stock and pour 2 cups liquid over vegetable mixture. Reserve remaining corn stock.
Purée in a blender until smooth. If too thick, add more corn stock.
Drizzle with best-quality olive oil and serve warm.