Pat the 3 chicken breasts dry and season them with 1 tsp salt and the black pepper.

Heat 1 tbsp olive oil in the large skillet over medium-high heat.

Sear the chicken breasts on all sides until golden and cooked through, about 10 to 12 minutes.

Transfer the cooked chicken to a plate and keep it aside.

Add the remaining 1 tbsp olive oil to the same skillet and heat it over medium heat.

Add the chopped yellow onion, 1 tsp salt, black pepper, and paprika to the skillet.

Sauté the onion mixture until softened, about 5 minutes.

Add the halved button mushrooms, whole grain mustard, soy sauce, dried oregano, and butter.

Stir the mushroom mixture and cook it for 5 minutes.

Pour the dry white wine into the skillet and scrape up any browned bits.

Simmer the wine until the alcohol evaporates and the liquid reduces, about 5 minutes.

Stir in the heavy cream, Parmesan cheese, and chopped fresh parsley.

Cook the sauce gently until thickened enough to coat a spoon, about 3 minutes.

Return the chicken breasts and any resting juices to the mushroom sauce.

Simmer the chicken in the sauce over low heat for 3 minutes, then serve hot.