Heat olive oil and butter in a large skillet over medium-high heat. Add the cubed chicken, season with salt, pepper, and paprika, and cook until golden brown. Remove the chicken from the skillet and set aside.
In the same skillet, add the chopped onion and cook until soft. Add the minced garlic and sliced mushrooms, sautéing until the mushrooms release their juices and become golden brown.
Pour in the chicken broth, scraping the bottom of the pan to lift any browned bits. Stir in the Dijon mustard and Worcestershire sauce, then return the chicken to the pan. Let it simmer for 5-7 minutes, allowing the flavors to meld.
Reduce the heat to low and stir in the sour cream and heavy cream. Mix well until the sauce is smooth and creamy. Let it cook for an additional 2-3 minutes without boiling.
Remove from heat and sprinkle with fresh parsley. Serve hot over egg noodles or rice. For another delicious chicken dish, check out Pan-Fried Tilapia.