01 - Pat chicken thighs dry using paper towels. Generously season both sides with salt, black pepper, smoked paprika, and dried thyme.
02 - Heat olive oil and unsalted butter together in a large skillet or Dutch oven over medium-high heat until shimmering. Place chicken thighs skin-side down and sear without moving for 6 minutes per side, or until deeply golden brown. Remove browned chicken and set aside on a plate.
03 - Add sliced yellow onions to the same pan. Cook, stirring periodically, until onions become soft and golden, about 8 minutes. Stir in minced garlic and cook for 1 additional minute until fragrant.
04 - Evenly sprinkle flour over cooked onions. Stir well and cook for 1 to 2 minutes to develop the flavor and eliminate any raw flour taste.
05 - Gradually pour chicken broth into the pan while whisking continuously to create a smooth gravy base and prevent lumps. Bring mixture to a gentle simmer.
06 - Nestle seared chicken thighs back into the skillet, skin-side up. Carefully spoon gravy and onions over the top of the chicken pieces.
07 - Cover pan with lid and let simmer on low heat for 25 to 30 minutes, or until chicken is thoroughly cooked and gravy has thickened.
08 - Taste gravy, adjust seasoning as necessary, and serve chicken thighs topped with generous ladles of rich onion gravy. Garnish with chopped fresh parsley if desired.