Slice chicken breasts in half horizontally to make them thinner. Season both sides of chicken breasts with garlic powder, oregano, and a pinch of salt and pepper.
Heat butter and oil in over medium-high heat in a large heavy duty pan or cast iron skillet. Add chicken breasts to the pan and cook 5-6 minutes per side. Remove chicken from pan and set aside.
To the same pan, add the mushrooms and onion to the pan and saute for 2-3 minutes or until tender. Add the garlic and a pinch of salt & pepper; saute for 1 minute or until fragrant.
Reduce heat to low and Add the heavy cream, parmesan cheese, and herbs. Simmer for 1-2 minutes or until sauce begins to thicken. Taste and add more salt if needed.
Return chicken along with its juices to the pan and cook for another 1-2 minutes. Serve with pasta, rice, salad, or veggies.