Preheat broiler to 450° F. Place the whole chiles in a dry cast iron skillet. Broil in the oven for 10 minutes, until evenly charred. Using tongs, turn the chiles over, and continue to broil for another 10 minutes until charred on both sides. Take chiles out of the oven and place in a large glass bowl. Cover the bowl tightly with plastic wrap and allow the chiles to steam for 10 minutes. Remove chiles from the bowl, and peel the skins off; they should slip off easily. Chop chiles into ¼-inch chunks. Place chopped chiles back in the large bowl and set aside.
Place the dry cast iron skillet on the stove over medium-high heat. Once the skillet is hot, add corn directly to the skillet. Stirring occasionally, heat corn until it is nicely browned, about 5-10 minutes. Place toasted corn in the bowl with the chiles.
Add the shredded cheese to the corn mixture and stir to combine (the cheese will start to melt). Add the next 4 ingredients, green onions through sour cream, to the large bowl with the chiles mixture. Mix gently to combine.
In a separate smaller bowl, roughly mash the avocado. Add the mashed avocado to the larger bowl with the other ingredients, and mix to combine.
Serve immediately with tortilla chips or fresh veggies for dipping.