Season the 3 chicken breasts with 1/2 teaspoon salt and black pepper on both sides.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat.

Sear the seasoned chicken breasts on all sides until golden and cooked through, about 8 to 10 minutes total.

Transfer the cooked chicken breasts to a plate and reserve.

Add the remaining 1 tablespoon olive oil to the same skillet over medium heat.

Add the chopped onion, 1 teaspoon salt, remaining black pepper, and paprika to the skillet.

Sauté the onion mixture until softened and fragrant, about 5 minutes.

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

Stir the mushroom mixture and cook for 5 minutes.

Pour in the 1/2 cup dry white wine and scrape the browned bits from the bottom of the skillet.

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

Stir the heavy cream, Parmesan cheese, and chopped fresh parsley into the mushroom sauce.

Cook the sauce gently until it thickens enough to coat a spoon, about 3 to 5 minutes.

Return the cooked chicken breasts to the creamy mushroom sauce.

Simmer the chicken in the sauce over low heat for 3 minutes, turning to coat.

Serve the creamy mushroom chicken with cooked rice.