Step 1Cut the cantaloupe into quarters, remove the seeds and peel. Using a mandoline, slice each quarter lengthwise as thinly as possible without having the fruit disintegrate. Divide the fruit equally and pile high onto four plates. Scatter one-fourth of the mint over each.
Step 2Drizzle one-half teaspoon lime juice and a tablespoon Port over each, along with a little black pepper.
Step 3Cut the prosciutto into quarter-inch julienne strips, and scatter one-fourth of it over the melon on each plate.