Place butter and oil in a large skillet over medium high heat. When the butter has melted and the oil is hot, add mushrooms, salt and pepper. Cook for 3 minutes or until golden, then transfer to a bowl.
If the skillet is looking dry, add a touch of oil and return to the stove.
Season pork on both sides with salt and pepper. Place in the skillet and cook for 3 minutes on each side, or until golden and cooked to your taste. Remove into a plate and cover loosely with foil.
Add white wine into skillet – it will sizzle. Cook for 1 minute, scraping the bottom of the skillet, or until you can no longer smell alcohol. Add remaining ingredients and mix (mustard will dissolve better once it comes to heat but use a whisk if necessary).
Simmer for 2 minutes or until it reduces and becomes like a thin syrup. Return mushrooms to the sauce. Adjust salt and pepper to taste, if its too sweet for your taste add a tiny touch of cider vinegar.
Serve pork, topped with the honey glaze and mushrooms, garnished with parsley if using.