Sear the Chicken:
Heat olive oil and butter in a large skillet over medium-high heat. Season chicken with salt and pepper, then sear until golden and just cooked through. Remove from skillet and set aside.
Sauté the Veggies:
In the same skillet, add chopped onion and mushrooms. Cook for 5–6 minutes until softened and lightly browned. Add garlic and paprika; cook for 30 seconds more.
Make the Sauce:
Sprinkle in flour and stir to coat vegetables. Slowly pour in chicken broth while stirring to avoid lumps. Bring to a simmer and let it thicken slightly.
Add Cream and Chicken:
Reduce heat to low. Stir in sour cream, heavy cream, and Dijon mustard if using. Return chicken to the pan and simmer gently for 2–3 minutes until heated through and sauce is creamy.
Serve:
Spoon over egg noodles or your preferred base. Garnish with fresh parsley.