In a large pot, boil the chicken in salted water until cooked through, about 20 minutes. Remove, cool, and shred the chicken.

In a skillet, heat the vegetable oil over medium heat. Add the sliced onion and cook until translucent, about 5 minutes.

Add the minced garlic and cook for another minute.

Add the chopped tomatoes, chipotle peppers, oregano, and cumin. Cook until the tomatoes break down, about 10 minutes.

Blend the sauce until smooth, then return it to the skillet and add the chicken broth. Simmer for 5 minutes.

Add the shredded chicken to the sauce, stirring to combine. Season with salt and pepper to taste.

Serve hot with tortillas and toppings of your choice.