Melt 6 tablespoons of butter with the olive oil in a large skillet over medium heat. Mix in the parsley and garlic and cook for a couple of minutes until fragrant. Add the mushrooms and asparagus and season with salt, pepper and onion powder; cook, stirring occasionally until asparagus is tender, about 5 minutes depending on the thickness. Place the scallops in the pan, and cook briefly on each side until lightly browned and the center is cooked through, about 3 minutes per side. Remove from the heat when scallops are just finished.