Husk the cobs of corn. Stand the ears of corn upright and cut off the kernels, slicing lengthwise down the ear. Reserve the kernels and place the cobs in a large pot, break the cobs in half to fit if necessary. Add water until the cobs are submerged. Please note, they will probably float a bit. Add the milk, half the salt and bring up to a boil over high heat. Reduce to a medium simmer for at least 15 minutes.

Chop up the onions. Place the butter in a large saute pan or pot over medium heat. As soon as it is melted add the onions and reduce the heat to low. Saute gently until the onions become translucent, about 5-10 minutes. Avoid browning the onions for this recipe, just add a splash of water or reduce the heat if the onions start to take on a bit of color or stick. Once the onions are translucent add in the corn kernels. Toss for another 5-10 minutes until the corn is just cooked through.

Place the corn and onions in a blender. Reserve about 1 cup of the corn if you want to have a few chunks in the soup. Add just enough of the cob liquid to get the corn and onions moving in the blender. Puree until smooth. For the silkiest soup, pour and push through a wire mesh strainer. Taste. Add more salt and the fresh black pepper to taste. Add the corn chunks and stir in the heavy cream, if desired.

Cool in the freezer for at least 15 minutes or for a few hours in the fridge until chilled. Serve cold with a squeeze of fresh lime or lemon to taste, if desired.