Slice the top and bottom off the pineapple, stand it on end, and slicing straight down, remove all the prickly peel. Cut the pineapple lengthwise into 8 wedges, slice off the hard core at the point of each wedge, then slice the wedges about 1/4-inch thick, making small fan-shaped pieces. Place the pineapple fans in a large non-metallic bowl, add the Port, and toss to mix. Cover and chill 3 to 4 hours. Add the mint, toss again, and chill 30 minutes long. To serve, spoon into stemmed goblets and if you like, sprig with fresh mint.
Recipe courtesy Jean Anderson, The Food of Portugal, Hearst Books, 1986