Start by making the tortilla chips. Adjust oven racks to the upper-middle and lower-middle positions and heat oven to 425º. Divide the tortillas evenly on two rimmed baking sheets. Drizzle each sheet with 2 tablespoons of oil, sprinkle with ¼ teaspoon of salt, and toss until evenly coated. Spread out the tortillas and bake, stirring occasionally, for about 15-20 minutes, or until the tortillas are golden and crisp. Rotate the pans halfway through.

While the tortillas are baking, toast the guajillos in a 12-inch cast-iron skillet set over medium heat. Cook for 2-6 minutes, stirring frequently. Transfer the guajillos to a blender and pulse until finely ground, 60-90 seconds. Add the tomatoes with their juice, ¾ cup onion, poblano, jalapeño, garlic, cilantro sprigs and ¾ teaspoon of salt to the blender. Blend until very smooth, an additional 60-90 seconds.

If needed, pound the ends of the chicken breasts to create an even thickness. Add the chile and tomato mixture to the skillet, along with the broth. Bring to a simmer over medium-high heat. Nestle the chicken into the sauce, then reduce heat to a gentle simmer. Cover and cook for 10-15 minutes, or until the chicken reaches 160º, flipping the chicken halfway through.

When the chicken is cooked through, transfer it to a cutting board and let cool slightly. Once cool, use two forks to shred the chicken into bite-size pieces. Meanwhile, increase the heat to medium and simmer the sauce until it has thickened and reduced to 4 cups, about 6 minutes.

Add the chicken back to the sauce and cook until warmed through, about 2 minutes. Remove from heat and stir in the tortillas. Cover and let sit until the tortillas have softened slightly, 2-5 minutes.

Sprinkle the chilaquiles with queso fresco, avocado, radishes, remaining onion and minced cilantro. Serve immediately.