Preheat the oven to 400 degrees. Line a rimmed baking sheet with parchment paper or a silicone baking mat. If the tomatillos are big, cut in halves or quarters. Place the tomatillos, peppers, onion, and garlic on the baking sheet. Drizzle with oil and season lightly with salt and pepper. Toss to coat. Roast for 20-30 minutes or until the tomatillos are fork tender, stirring once.
Peel off any skin that is blistered from the poblano peppers. Place the peppers, tomatillos, onion, and garlic in a food processor or blender along with any juices that have accumulated and pulse a few times to just break them up a bit. Add 2 cups chicken broth and pulse a few more times until the mixture is blended but still has texture. Pour into a large pot.
Add the agave, chicken, and remaining 2 cups chicken broth to the soup and heat over medium heat for 5-7 minutes or until heated through. Keep warm.
Stir the lime zest and juice into the sour cream.
Ladle the soup into bowls, divide the corn chips among the bowls, drizzle with the sour cream, the top the soup with avocado slices and cheese crumbles. Serve with lime wedges.