01 - Pat chicken thighs dry with paper towels. Generously season both sides with salt, black pepper, smoked paprika, and thyme.
02 - Heat olive oil and unsalted butter in a large skillet or Dutch oven over medium-high heat until the butter foams. Place chicken thighs skin-side down and sear until the skin is deeply golden, about 6 minutes per side. Remove chicken to a plate and keep warm.
03 - Add sliced onions to the same pan. Cook, stirring occasionally, until onions are soft and deeply golden, about 8 minutes. Add minced garlic and sauté for 1 minute until fragrant.
04 - Sprinkle flour evenly over the onions. Stir continuously and cook for 1 to 2 minutes, ensuring the flour is well combined and lightly toasted.
05 - Gradually pour in chicken broth, whisking constantly to prevent lumps. Bring to a gentle simmer, scraping up any browned bits from the pan.
06 - Return the seared chicken thighs to the skillet, skin-side up. Spoon some onion gravy over the chicken pieces.
07 - Cover the skillet or Dutch oven. Simmer on low heat for 25 to 30 minutes, until chicken is cooked through and gravy is thickened.
08 - Taste the gravy and adjust seasoning with additional salt or pepper if necessary. Serve each chicken thigh generously ladled with onion-rich gravy. Garnish with chopped fresh parsley if desired.