Boil the chicken breasts in a pot of water until fully cooked.
Once cooked, remove from the pot and let cool. Shred the chicken using two forks and set aside.
Then take a large skillet and heat the vegetable oil over medium heat. Add the sliced onions and cook until they are translucent.
Now add the minced garlic and cook for an additional minute.
Add the diced tomatoes, chipotle peppers, oregano, and cumin to the skillet and mix well.
Add the shredded chicken to the skillet and stir until the chicken is well-coated with the sauce. Season with salt and pepper to taste. Let simmer for 10 minutes.
Warm the corn tortillas on a skillet or directly over the flame until they are soft and pliable.
Finally, assemble the tacos by placing a generous amount of shredded chicken on each tortilla.
Garnish with cilantro, a squeeze of lime, queso fresco, and avocado slices if desired.
Serve immediately and enjoy!
