1. Cut prosciutto crosswise into 1/2-inch strips. In a 6- to 8-inch pan over high heat, stir prosciutto until crisp and well browned, about 5 minutes. Drain on paper towels.
2. In a large bowl, whisk together the vinegar, oil, and mustard. Season with salt and pepper to taste. Add spinach and blackberries and mix gently to coat.
3. Using a vegetable peeler or cheese slicer, shave thin slices of the cheese over salad. Add prosciutto. Mix gently.
Note: Nutritional analysis is per serving.