01 - Pat chicken thighs dry. Liberally season with salt, black pepper, smoked paprika, and thyme on all sides.
02 - Heat olive oil and butter together in a large skillet or Dutch oven over medium-high heat until shimmering.
03 - Place the seasoned chicken thighs skin-side down in the pan. Sear without moving until deep golden brown, about 6 minutes per side. Transfer browned chicken to a plate.
04 - Add the sliced onions to the same pan. Cook, stirring occasionally, until onions are soft and caramelized, about 8 minutes. Stir in garlic and cook for 1 additional minute.
05 - Sprinkle flour evenly over the onions. Stir constantly and cook for 1 to 2 minutes, allowing the raw flour to cook off.
06 - Gradually pour chicken broth into the pan while whisking to prevent lumps. Bring mixture to a gentle simmer, ensuring a smooth gravy forms.
07 - Nestle the seared chicken thighs skin-side up into the gravy. Spoon onions and gravy over the chicken pieces.
08 - Cover and reduce heat to low. Simmer gently for 25 to 30 minutes until chicken reaches 74°C (165°F) internal temperature and gravy thickens.
09 - Taste the gravy and adjust seasoning with additional salt and pepper as needed.
10 - Serve chicken thighs generously topped with onion gravy. Garnish with chopped parsley if desired.