Heat the olive oil in a large, deep skillet over medium high heat.
Season the chicken thighs with salt and pepper on both sides.
Add the chicken to the pan and cook for 4-5 minutes until golden brown. Flip the chicken over and cook for an additional 4-5 minutes. Transfer to a plate and keep warm.
Add the onion to the pan and cook for 2-3 minutes or until beginning to soften.
Stir in the garlic and cook for 1 minute longer.
Transfer the onion mixture to the pitcher of a blender.
Add the tomatoes, chipotle chili, adobo sauce, chicken stock, cumin, cayenne and paprika to the blender. Close the lid and puree until smooth. Season with salt and pepper, to taste.
Return the chicken to the pan and pour the sauce over the chicken.
Cover and cook over low heat for 20-30 minutes or until the chicken shreds easily with a fork.
Remove the chicken to a cutting board or platter. Using two forks, shred the chicken and return to the pan.
Cook for an additional 5-10 minutes uncovered.
Serve over rice or on corn tortillas to make Chicken Tinga Tacos and sprinkle with cilantro, if desired.