Add 2 cups of water and leftover corn cobs to a pot. Simmer for 20-30 minutes covered. Remove corn cobs and set aside.
While the corn stock is cooking, heat small saucepan to medium heat. Add butter and onion. Sweat onions with a pinch of salt until translucent, about 4-8 minutes.
Add corn kernels to pot and saute for another 2-4 minutes with another pinch of salt. Reserve a couple tablespoons for garnish.
Transfer cooked corn to a blender with the corn stock. Blend until completely smooth.
Serve hot and top with reserved corn garnish and optional garnish of herbs, fresh chopped or dried. Makes about 3 cups of soup.
Notes
Use fresh corn. If using frozen corn, add a pinch of sugar. Avoid canned corn if possible.
Substitute homemade corn stock with vegetable stock.
Use a Vitamix for the smoothest puree.
Take care when blending hot liquids, since the steam can cause the cap to pop off. Hold the top and pulse gently to get the soup started.