Season chicken with salt and pepper. Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add chicken and sear for 3-4 minutes per side until lightly browned.

Reduce heat to medium. Add diced onion and cook until softened, about 3-4 minutes. Stir in minced garlic, the minced chipotle peppers, and the reserved adobo sauce. Cook for 1 minute until fragrant.

Add ground cumin, dried oregano, chicken broth, and lime juice. Bring to a simmer, then reduce heat to low, cover, and cook for 15-20 minutes, or until chicken is cooked through and easily shreddable.

Remove chicken from the skillet and shred using two forks. Return shredded chicken to the skillet with the sauce. Stir well to coat and keep warm.

**Air Fryer Method:** Preheat air fryer to 375°F (190°C). Lightly brush or spray each side of the corn tortillas with olive oil and sprinkle with a pinch of salt. Place tortillas in a single layer in the air fryer basket (work in batches if necessary) and cook for 4-6 minutes, flipping halfway, until golden brown and crispy.

**Oven Method:** Preheat oven to 400°F (200°C). Lightly brush or spray each side of the corn tortillas with olive oil and sprinkle with a pinch of salt. Place tortillas on a baking sheet in a single layer and bake for 8-12 minutes, flipping halfway, until golden brown and crispy.

Set crispy tostada shells aside.

If using, warm the refried beans according to package instructions.

Spread a thin layer of refried beans onto each crispy tostada shell (optional).

Top generously with the warm chipotle shredded chicken.

Add shredded lettuce, sliced avocado or guacamole, and a sprinkle of crumbled cotija cheese.

Drizzle with Mexican crema or sour cream, add a dollop of salsa, and garnish with pickled red onions and fresh cilantro, if desired. Serve immediately.