Pat chicken dry and season with salt, pepper, and paprika. Heat olive oil or butter in a large skillet over medium-high heat. Add chicken in a single layer and cook 5–6 minutes, stirring once or twice, until golden and just cooked through. Transfer to a plate.

If the pan looks dry, add a little more oil or butter. Add onion with a pinch of salt and cook 2–3 minutes until softened. Stir in garlic and cook 30–60 seconds until fragrant.

Add sliced mushrooms, spread out, and cook 4–5 minutes until they release liquid and develop golden edges.

Sprinkle flour over the mushrooms and stir 30–60 seconds to coat. Whisk in the chicken broth gradually, scraping up browned bits to make a smooth, lightly thickened sauce.

Stir in dried thyme (or oregano), Dijon, and Worcestershire (or soy). Return chicken and any juices to the pan; simmer gently 2–3 minutes so flavors meld and sauce reduces slightly.

Reduce heat to low. Off heat, stir in sour cream (or Greek yogurt) until smooth and silky; return to low heat if needed to warm through—do not boil. Adjust salt and pepper and add a small squeeze of lemon if you like extra brightness.

Serve over hot egg noodles, rice, or mashed potatoes. Garnish with chopped parsley.