In a large bowl, soak the chicken thighs in buttermilk for at least 1 hour to tenderize the meat. For best results, refrigerate overnight.
In a shallow dish, combine the flour, garlic powder, onion powder, smoked paprika, salt, and pepper.
Remove the chicken from the buttermilk, allowing excess to drip off. Dredge each thigh in the seasoned flour mixture, shaking off any excess flour.
Heat olive oil and butter in a large skillet over medium-high heat. When hot, add the chicken thighs skin-side down. Cook for about 5-7 minutes until golden brown, then flip and cook the other side for another 5-7 minutes. Remove the chicken and set aside.
In the same skillet, add the sliced onion and bell pepper. Sauté for about 5 minutes until softened. Add the minced garlic and cook for an additional minute.
Pour in the chicken broth, Worcestershire sauce, and thyme. Stir to combine and scrape up any bits from the bottom of the skillet.
Return the chicken thighs to the skillet, skin-side up. Reduce the heat to low, cover, and let simmer for about 30 minutes until cooked through and tender.
Remove the chicken and let it rest for a few minutes. Increase the heat and let the sauce reduce slightly for about 5 minutes if you prefer a thicker gravy.
Serve the chicken with the smothered sauce over rice or mashed potatoes, garnished with fresh parsley.
Notes
For best results, soak the chicken in buttermilk overnight.