FOR THE SOUP:
2 tablespoons vegetable oil
1 large yellow onion, finely chopped
4 cloves garlic, finely chopped
1 jalapeño, seeds removed, finely chopped
Kosher salt and freshly ground pepper
1 ½ teaspoons chile powder
2 chipotles in adobo, finely chopped
1 (28-ounce) can whole peeled tomatoes, drained and crushed
4 cups vegetable broth
2 cups corn kernels, fresh or frozen and thawed
FOR THE TORTILLAS AND ASSEMBLY:
2 cups vegetable oil
8 small corn tortillas, cut into 1/4-inch strips
Kosher salt
1 avocado, pitted and cut into 1/2-inch pieces
¾ cup crumbled queso fresco or shredded Cheddar or Monterey jack
¾ cup sour cream or crema
½ cup chopped cilantro
¼ red or yellow onion, finely chopped
Lime wedges, for serving
Heat oil in a large, heavy-bottomed pot over medium heat. Add onion, garlic and jalapeño and season with salt and pepper. Cook, stirring occasionally, until onion is softened and translucent, 5 to 8 minutes. Add chile powder and stir to coat. Cook a minute or two to toast the spices, then add chipotles and tomatoes. Season with salt and pepper and cook, stirring occasionally, until the tomatoes start to caramelize a bit on the bottom of the pot, concentrating their flavor.
Add vegetable broth, corn and 2 cups of water. Bring to a simmer and reduce heat to low. Simmer until flavors meld and broth tastes rich and flavorful, 15 to 20 minutes.
Heat oil in a large cast-iron or stainless-steel skillet or heavy-bottomed pot. Bring oil to 375 degrees and working in batches, fry tortilla strips until light golden brown and crisp, 2 to 3 minutes. Transfer to a paper towel-lined plate and season with salt.
Place about 3/4 of the tortilla strips into broth and stir to submerge and soften for a few minutes. Divide soup among bowls and top with avocado, cheese, sour cream, cilantro, onion and remaining fried tortilla strips. Serve lime alongside for squeezing.