Wrap each ear of corn in aluminum foil and place in a 350°F oven to roast for 30minutes. Halfway through cooking, rotate the corn so it does not brown
Remove the corn from the oven and allow to cool and then slice the corn off each cob. Reserve the kernels in the refrigerator for later.
With a large knife chop each cob in half and place in a pot with the 4 cups of water. Bring the water to a boil and then turn down to a simmer and allow to cook for 45 minutes.
Strain the corn stock through a fine-mesh strainer and cool until chilled
Place the corn kernels (about 4 cups), corn stock(2 cups worth), olive oil, vinegar, and salt in a blender and blend on high still smooth. When in doubt, blend for an extra minute or two to ensure all of the corn is pureed. Pass the soup through a fine-mesh strainer using a spoon or ladle to push it through. Keep the soup in the refrigerator until it is served.
If using the shrimp, marinate them for a minimum of 30 minutes in3 table spoons lime juice, 2 tablespoons olive oil and a pinch of salt.
Place the shrimp in bowls, sprinkle with the red pepper and scallion, and top with the soup.