Crisp the Tortillas: Heat the oil in a large pot or Dutch oven over medium-high heat.
Once hot, fry the tortilla strips in batches until golden and crisp, about 2-4 minutes. Use a slotted spoon to transfer them to a paper towel-lined plate and season immediately with salt.
Set aside.
Sauté the Aromatics: Carefully pour out all but 2 tablespoons (30 ml / 1 fl oz) of oil from the pot.
Reduce the heat to medium and add the sliced onion and garlic.
Cook, stirring occasionally, until softened and golden, about 10 minutes.
Roast the Vegetables: While the onions cook, turn on your broiler.
Place the fresh tomatoes and poblano chiles on a baking sheet and broil a few inches from the heat until the skins are charred and blistered, about 5-8 minutes total, flipping once.
Once cool enough to handle, peel, stem, and seed the chiles. (If using canned tomatoes, you can skip this step).
Simmer the Soup Base: Add the charred tomatoes and chiles to the pot with the onions and garlic. Use the back of a spoon to crush the tomatoes.
Season with salt, pepper, and oregano.
Pour in the vegetable stock, bring to a gentle simmer, and cook for 20-30 minutes to allow the flavors to meld.
Blend and Finish: Let the soup cool slightly. Use an immersion blender to purée the soup until smooth (or carefully transfer in batches to a regular blender). Return the soup to the pot over medium heat.
Stir in most of the fried tortilla strips (reserving some for garnish) and simmer for another 3-5 minutes, just until they begin to soften.
Squeeze in fresh lime juice to taste, adjust seasoning, and serve immediately with your favorite garnishes.
Don't skip the broiling step for the fresh tomatoes and chiles; charring them is the key to developing a deep, smoky flavor that makes this soup truly special.
