Combine garlic, onion, vinegar, ancho chili powder, cumin, oregano, 2 tbsp of oil, salt, pepper, chipotle pepper, and adobo sauce in a blender or food processor and puree until smooth.
Put the chicken thighs into a large resealable bag and pour the marinade over them. Seal the bag and massage to coat the chicken evenly. Refrigerate for 2 to 3 hours or overnight for best flavor.
If grilling, heat your grill to medium-high and oil the grates with 1 to 2 tablespoons of oil. Cook the chicken for 3 to 4 minutes on each side until the internal temp hits 165°F. You might need to do this in batches to prevent crowding.
Let the cooked chicken rest briefly before chopping it roughly for serving.
Alternatively, for stovetop cooking, warm 2 tablespoons of oil in a skillet over medium-high heat. Sear the chicken thighs for 3 to 4 minutes per side until cooked through (165°F internal temp), working in batches if needed.
Rest the chicken and roughly chop.
For oven preparation, preheat the oven to 450°F. Arrange the chicken in a baking dish and bake for 18 minutes.
Cover the dish with aluminum foil and return to the oven for an additional 4 to 5 minutes.
Allow the chicken to rest before roughly chopping it for use.
