Slice both ends off the mango, revealing the long, slender seed inside. Set the fruit upright on a work surface and remove the skin with a sharp knife. Then (unless you’re a lefty) hold it in your left hand, palm facing you. With a very sharp knife in your right hand, score the mango vertically all the way down to the large pit, making the cuts about 1/8 inch apart. When the side facing you is completely scored, shave off juliennes with a vegetable peeler. Repeat on the other side of the mango. You’ll have juliennes as thin as angel hair pasta.