01 - Season chicken strips evenly with salt and pepper on all sides.
02 - Heat 1 tbsp butter and olive oil in a large skillet over medium-high heat. Add chicken and sauté until golden brown and cooked through, approximately 5-7 minutes. Transfer to a plate and cover to keep warm.
03 - Add remaining 1 tbsp butter to the same pan. Cook onion for 2-3 minutes until translucent. Add mushrooms and cook until browned and liquid has evaporated, about 5 minutes. Stir in garlic and cook for 1 minute until fragrant.
04 - Sprinkle flour over vegetables, stirring constantly to coat evenly. Cook for 1 minute to remove raw flour taste.
05 - Gradually whisk in chicken broth while stirring to prevent lumps. Add Dijon mustard, paprika, and Worcestershire sauce. Simmer for 3-4 minutes until sauce begins to thicken slightly.
06 - Reduce heat to low. Stir in sour cream until fully incorporated and smooth. Return chicken with accumulated juices to skillet. Simmer gently for 2-3 minutes until heated through. Do not boil to prevent sauce from separating.
07 - Taste sauce and adjust salt and pepper as needed.
08 - Garnish with fresh parsley and serve immediately over egg noodles, rice, or mashed potatoes.