01 - Pat chicken thighs dry thoroughly. Generously season both sides with salt, black pepper, smoked paprika, and dried thyme.
02 - Heat olive oil and unsalted butter in a large skillet or Dutch oven over medium-high heat. Arrange chicken thighs skin-side down and sear until the skin is golden and crisp, about 6 minutes per side. Transfer chicken to a plate and set aside.
03 - Reduce heat to medium. In the same pan, add sliced onions. Sauté, stirring occasionally, until onions soften and become deeply golden, about 8 minutes. Add minced garlic and cook for 1 minute, stirring constantly.
04 - Sprinkle flour evenly over onions. Stir and cook for 1 to 2 minutes to remove raw flour taste.
05 - Gradually pour in the chicken broth, whisking constantly to prevent lumps. Bring mixture to a gentle simmer.
06 - Nestle chicken thighs skin-side up into the skillet. Spoon some onion gravy over the top of each piece.
07 - Cover and gently simmer on low heat for 25 to 30 minutes, until chicken is fully cooked and gravy has thickened.
08 - Taste gravy and adjust seasoning with additional salt and pepper if needed.
09 - Arrange chicken on plates and ladle rich onion gravy over the top. Garnish with chopped fresh parsley if desired.