01 - Pat chicken breasts dry with paper towels. Season both sides generously with salt and pepper, pressing gently to help the seasoning adhere.
02 - Heat olive oil in a large skillet over medium-high heat until shimmering. Add chicken breasts and sear for 3 to 4 minutes per side until golden brown and cooked through. Transfer to a plate and tent loosely with aluminum foil.
03 - Reduce heat to medium. Add butter to the skillet and swirl to coat. Add sliced mushrooms and sauté for 5 to 6 minutes, stirring occasionally, until browned and all liquid has evaporated.
04 - Stir in minced garlic and cook for 1 minute until fragrant, being careful not to burn it.
05 - Pour in heavy cream, chicken broth, and Dijon mustard. Add thyme and oregano. Stir to combine and bring to a gentle simmer. Cook for 3 to 4 minutes, stirring occasionally, until the sauce thickens slightly and coats the back of a spoon.
06 - Return chicken breasts to the skillet, nestling them into the sauce. Simmer for 2 to 3 minutes until heated through. Stir in chopped parsley. Taste and adjust seasoning with additional salt and pepper if needed.
07 - Transfer chicken to serving plates. Spoon mushrooms and creamy sauce generously over the top. Garnish with additional fresh parsley if desired.