Pat the chicken thighs completely dry using paper towels so they brown properly instead of steaming. Season both sides evenly with salt and black pepper, making sure every piece is coated well for balanced flavor throughout the dish.

Place a large skillet or Dutch oven over medium-high heat and add the butter and olive oil together. Allow the butter to melt fully and become lightly foamy before adding the chicken.

Carefully place the chicken thighs into the hot skillet in a single layer. Let them cook undisturbed for several minutes so a deep golden crust develops. Flip the chicken and brown the second side as well.

Transfer the browned chicken thighs onto a plate and set aside temporarily. Leave all the flavorful browned bits in the pan because they will dissolve into the sauce and create even more flavor.

Add the sliced onions directly into the skillet. Stir occasionally while cooking over medium heat until the onions soften, turn golden, and develop sweetness.

Stir in the minced garlic and cook briefly until fragrant. Sprinkle the paprika evenly over the onions and stir immediately so the spices bloom in the warm fat.

Sprinkle the flour over the onion mixture and stir thoroughly until no dry flour remains visible. Slowly pour in the chicken broth while stirring continuously to prevent lumps from forming.

Return the chicken thighs and any accumulated juices back into the skillet. Spoon some sauce over the chicken, partially cover the pan, and simmer gently for about 15 to 20 minutes.

Lower the heat to prevent curdling. Stir a spoonful of warm sauce into the sour cream first to temper it, then slowly mix the sour cream into the skillet.

Taste the sauce and adjust seasoning if necessary. Sprinkle with fresh parsley and serve hot over noodles, mashed potatoes, rice, or crusty bread.