For the basil drizzle: Combine the basil, parsley, salt, red pepper flakes, garlic, lemon juice and chile in a mini food processor and pulse to make a chunky paste. Add the olive oil and process until smooth and bright green.
For the prosciutto, cantaloupe and butter sandwich: Spread the butter on both cut sides of the baguette. Drizzle the bottom piece with a tablespoon or so of the basil drizzle. Layer the prosciutto and cantaloupe on the bottom piece of the baguette, ruffling and folding the prosciutto as you go. Drizzle a tablespoon of the basil drizzle over the top. Drizzle the cut side of the top piece with 1/4 cup or so of the basil drizzle. Place the top piece of baguette on the prosciutto and cantaloupe and cut into 2 sandwiches using a serrated knife. Serve the extra basil drizzle on the side or reserve for another use.