This soup is a new favorite in my household. The recipe comes from Pati's Mexican Table. I added the potatoes and puréed it with a stick blender because that just sounded right. This is definitely on the spicy side, but it's so good!
Arrange poblano peppers on a baking sheet & roast under the oven broiler for 5 minutes a side. Remove peppers to ziplock bag. Seal the bag and let them "sweat" for about 20 minutes. Peel, stem, and seed the peppers. Cut them into largish dice.
Heat the oil in a Dutch oven over medium heat. Sauté the onions until just beginning to color, five minutes or so. Add the garlic and salt & sauté about a minute. Add the peppers and cook for another minute or two. Add the potatoes and the chicken broth. Cover halfway, bring to a boil, reduce to a simmer & cook 30 minutes.
At the end of the 30 minutes, use a stick blender to reduce the soup to a rough purée (I like it a little chunky). Add the corn and bring back to a simmer to heat the corn. Turn off the heat, stir in the milk, and serve.