Heat a dry pan over medium heat on the stove.
Add the pine nuts and toast until golden and fragrant while stirring constantly, about 4-5 minutes.
Combine watermelon, cucumber, and mint in a large bowl, then add the toasted pine nuts.
Whisk the dressing in a separate bowl and pour over the salad. Gently toss together.
Drape with prosciutto slices before serving.
