Add in half of the Parmesan and grated mozzarella, onion powder, mushrooms, macaroni and truffle oil to the thickened sauce. Mix. Pour into a baking dish. Combine the Parmesan, panko crumbs, pepper and a pinch of salt in a bowl. Top the macaroni with the panko mix. Grill under the broiler for 5 min or until starting to brown.