Slice stem off poblano and cut pepper in half. Remove seeds and membranes. Flatten pepper halves on baking sheet and broil for 10 minutes or until charred. Remove from oven and place in a zip top plastic bag for 10-15 minutes. Remove and discard charred skin from peppers. Dice poblano pepper flesh and place in a mixing bowl.
If you are using fresh corn, cook it in boiling water for 2-3 minutes, or until tender.
Mix the corn (if using frozen, add it here) and the remaining ingredients in the mixing bowl with the poblano pepper. Stir and serve.
You can also roast the poblano pepper over a gas grate on the stovetop or on the grill.
Stovetop: Turn one of the burners on your stovetop to high. Place the pepper right on the grate. (You want the skin to char.) Use a pair of metal tongs to turn the pepper over the flame until the entire pepper is black. Place the pepper in a zip top bag or in a container with fitted lid for at least 10 minutes or until cool enough to handle.
Grill: The directions for roasting peppers on a grill is very similar to roasting on a stovetop: heat the grill and place the peppers directly on the grates. Turn occasionally until peppers are charred. Place in zip top bag or container with lid.