1. In a mixing bowl, whisk together the balsamic vinegar, honey, whole grain Dijon mustard, and garlic until combined. Drizzle in the olive oil very slowly, whisking continuously so that the vinaigrette emulsifies and thickens. Add the Parmesan cheese. Season the vinaigrette with salt and pepper (it should taste somewhat salty). Reserve until serving.
2. Preheat the oven to 300°F. Lay the prosciutto onto a baking sheet in one layer. Bake until crispy, about 20 minutes. Let cool. Crumble each piece into bite-sized pieces.
3. Meanwhile, take the head of radicchio and cut in half lengthwise. Place each half flat side down and slice the radicchio into ¼” strands, working toward the root end. Discard the root. Soak the strands in cold water for about 30 minutes. Drain and let the radicchio completely dry in one layer on a paper towel-lined tray. While the radicchio soaks, cut the red-leaf lettuce in similar strands, rinse, and dry. Take the fennel and shave it into thin strips on a mandolin, discarding the core.
4. To assemble the salad, combine the radicchio, red leaf lettuce, and shaved fennel in a large mixing bowl. Add half of the balsamic vinaigrette and toss to combine. Add enough more to completely coat the greens, reserving any extra for a later use.

To Serve

1. Serve each plate of salad with a generous grating of Parmesan cheese over top (the more the better). Garnish with the crispy prosciutto pieces.