If using bacon, cook bacon until crisp; drain, reserving drippings. Finely crumble bacon. Set aside. Using ½ tsp shortening for each cup, grease the bottom and sides of 6 cups of a popover pan. Set aside.
In a mixing bowl combine eggs, milk and bacon drippings. Add flour, bacon and Parmesan cheese. Beat with a rotary beater or wire whisk until mixture is smooth. Fill the prepared cups half full. Bake at 400°F for 40 minutes or until very firm.
Immediately remove popovers from the oven and prick the top of each with a fork to allow steam to escape. Serve hot.