Balsamic Dressing:
Whisk together the vinegar, sugar, mustard, salt and pepper.
Whisk in olive oil in a thin, steady stream until dressing is emulsified.
Salad:
Preheat oven to 350 degrees and line a sheet pan with parchment paper. Lay the prosciutto slices in a single layer on the prepared sheet pan and bake for about 15 mins.
Turn your grill onto high heat. Cut the watermelon into 1 inch slices and remove rinds. Brush the watermelon with the olive oil and season with salt and pepper.
Grill until charred grill marks show on one side, about 3 mins. Flip over and grill an additional 3 mins or until charred marks show. Cut watermelon into chunks.