01 - Pat the chicken thighs dry thoroughly. Season liberally on all sides with salt, black pepper, smoked paprika, and dried thyme.
02 - Heat the olive oil and unsalted butter in a large skillet or Dutch oven over medium-high heat. When hot, arrange the chicken thighs in the pan, skin-side down, and sear until deeply golden, about 6 minutes per side. Transfer the seared chicken to a plate and set aside.
03 - Using the same pan, add the sliced yellow onions. Cook, stirring occasionally, until soft and caramelized, about 8 minutes. Add minced garlic and cook for 1 minute until fragrant.
04 - Sprinkle the flour evenly over the onions and stir to coat. Stir continuously and cook for 1 to 2 minutes to dissipate the raw flour taste.
05 - Gradually pour the chicken broth into the pan while whisking to prevent lumps. Bring the sauce to a gentle simmer, ensuring a smooth, cohesive gravy texture.
06 - Nestle the seared chicken thighs, skin-side up, back into the gravy. Spoon some gravy and onions over the chicken for even coverage.
07 - Cover the skillet or Dutch oven and simmer over low heat for 25 to 30 minutes, until the chicken is cooked through and the gravy is thickened.
08 - Taste the gravy and adjust seasoning with additional salt or pepper if needed.
09 - Divide the chicken thighs among plates. Ladle the onion gravy generously over the top and finish with chopped fresh parsley if desired.