Flatten the pork tenderloin patties with the flat side of a French knife. Combine the egg and milk together in a small bowl, blending well. Measure cornflake crumbs onto a sheet of wax paper. Dip each pork tenderloin patty in the egg mixture and then lightly coat each in crumbs. (This step may be eliminated, if desired.)
In a large heavy skillet, heat oil over moderate heat. Brown coated or uncoated pork tenderloin patties, both sides, in hot oil over moderate to high heat, about 5 to 7 minutes total. Season browned patties with salt and pepper to taste. Transfer pork tenderloin patties to a platter. Reduce heat slightly. Add mushrooms to hot pan drippings in skillet and sauté over moderate heat until crisp tender. Drain off any excess pan drippings.
Combine remaining ingredients, except garnish, in a small bowl, blending well; evenly pour mixture over mushrooms, mixing gently but well. Return pork tenderloin patties to skillet, coating patties well with mushroom sauce. Reduce heat to a simmer, partially cover, and simmer about 20 to 25 minutes until pork tenderloin patties are fork tender and flavors well blended. Adjust seasoning to taste.
To serve, arrange two pork tenderloin patties on each dinner plate; spoon mushroom sauce over each, dividing evenly. Garnish each serving with a sprig of fresh basil.