Pre-heat oven to 350° degrees.
On a baking sheet, lay the slices of prosciutto in a single layer. Bake until prosciutto becomes firm and golden, about 15–20 minutes. The prosciutto may not be crisp in the oven, but, don’t worry, as it cools it will crisp up nicely.
While the prosciutto is cooking, toss the peaches, fennel, and arugula together in a large bowl.
In a small bowl, whisk the vinegar and oil together, adding the oil in a slow stream to create an emulsion. Season to taste with salt and pepper.
Toss the peaches, fennel and arugula together with the dressing and arrange on a serving platter or on plates.
Garnish the salad with the mozzarella and prosciutto.