01 - Pat chicken thighs dry. Generously season with salt, black pepper, smoked paprika, and dried thyme on both sides.
02 - Heat olive oil and unsalted butter in a large skillet or Dutch oven over medium-high heat. Place chicken thighs skin-side down and sear until the skin is golden brown, about 6 minutes per side. Remove chicken thighs and set aside.
03 - In the same pan, add sliced yellow onions. Cook, stirring occasionally, until soft and golden, about 8 minutes. Add minced garlic and sauté for 1 additional minute.
04 - Sprinkle all-purpose flour or gluten-free flour over the onions. Stir and cook for 1 to 2 minutes until flour is lightly toasted and loses its raw flavor.
05 - Gradually pour in chicken broth while whisking continuously to prevent lumps from forming. Bring the mixture to a gentle simmer.
06 - Carefully return seared chicken thighs, skin-side up, to the skillet. Spoon some of the onion gravy over the chicken pieces.
07 - Cover the skillet and simmer on low heat for 25 to 30 minutes, until the chicken thighs are fully cooked and the gravy has thickened.
08 - Taste gravy and adjust seasoning if necessary. Serve hot, topped with onion gravy and a sprinkle of fresh chopped parsley if desired.