- Whisk together all dressing ingredients in a small bowl and set aside.
- Heat a small skillet over medium-high. Add the slices of prosciutto and cook about 2 minutes on each side, until it begins to brown and the edges crisp. Transfer to a plate lined with a paper towel and set aside.
- Add the arugula to a large bowl. Drizzle in 1 to 2 tablespoons of the dressing and toss the greens well in the dressing. Add the oranges, grapefruit, and mozzarella. Toss together gently.
- Chop the prosciutto into small pieces and add half to the bowl.
- Plate the salad by layering and piling all the ingredients on a serving platter or in a serving bowl. Top with the remaining prosciutto. Serve the remaining dressing on the side.