Place the raw chicken breasts in a pot and cover with water. Bring to a boil and cook for 10-15 minutes, until the chicken is fully cooked through. Transfer the chicken to a bowl and let cool slightly, then use two forks to shred; set aside.

In a blender, combine the crushed tomatoes, chipotle peppers, and a pinch of salt. Blend until smooth and set aside.

Heat the oil in a skillet over medium heat. Add the onions and garlic and cook for 5-8 minutes, until softened. Pour the blended chipotle-tomato mixture into the skillet and stir in the oregano and thyme. Simmer for 7-8 minutes, until the sauce thickens and deepens in color.

Add the shredded chicken to the sauce and stir to coat. Cook for 1-2 minutes longer, until heated through. Serve.