Heat olive oil in a large heavy-bottomed skillet over medium-high heat. Season chicken with salt, pepper, and paprika. Add chicken in a single layer and sear for 4–5 minutes until golden brown. Flip and cook another 3–4 minutes. Remove and set aside.

In the same pot, melt butter. Add diced onion and cook until translucent and soft, about 3 minutes. Stir in garlic and cook until fragrant, about 30 seconds.

Add sliced mushrooms in an even layer. Let them cook undisturbed for 3–4 minutes to develop a deep golden color before stirring. Continue cooking until mushrooms are browned and moisture has evaporated.

Sprinkle flour over the mushroom mixture and stir constantly for 1 minute to eliminate raw flour taste.

Slowly pour in chicken broth while stirring to prevent lumps. Add Dijon mustard and Worcestershire sauce. Bring to a gentle simmer.

Return chicken and its juices to the skillet. Add egg noodles and stir so they are mostly submerged in liquid.

Cover and simmer for 10–12 minutes, stirring occasionally, until noodles are tender and sauce thickens naturally.

Reduce heat to low. Stir in room-temperature sour cream until smooth and creamy. Do not boil after adding sour cream.

Garnish with fresh parsley and serve warm.