Step 1:

• Preheat your oven to 350°F (about 175°C).
• Next, lay out your tortillas on a baking sheet.
• Give them a light spray with cooking spray on both sides.
• Pop them in the oven for about 12 minutes.
• This will give them a nice crispy texture without using too much oil.

Step 2:

• Place chicken breasts in a saucepan and cover with water.
• Bring to a boil, reduce heat, and simmer for 15-20 minutes until cooked through.
• Remove chicken from the pan and shred it with two forks. Set aside.

Step 3:

• In a blender or food processor, combine onion, garlic, chipotle peppers, canned diced tomatoes, ground cumin, dried oregano, salt, and black pepper.
• Blend until smooth.
• In a large skillet, heat the tomato mixture over medium heat for 5 minutes.

Step 4:

• Add the shredded chicken to the skillet and stir it into the tomato mixture until the chicken is well-coated with the sauce.

Step 5:

• Spread a thin layer of refried beans onto each corn tostada.
• Top each tostada with a generous spoonful of the chicken tinga mixture.
• Sprinkle with crumbled queso fresco, chopped fresh cilantro, and sliced avocado.
• Serve with lime wedges on the side.
• Enjoy your delicious Chicken Tinga Tostadas!