- Combine ingredients for pesto in a food processor and blend until well combined. Transfer mixture to a small bowl. Set aside.
- Preheat oven to 375ºF and line a small baking sheet with parchment paper. Lay slices of prosciutto on baking sheet and bake for 12-15 minutes. Remove from oven and cool on baking sheet while preparing mac and cheese. Increase oven temperature to 425ºF.
- In the meantime, bring 8 cups of water to a boil in a large pot. Season water with ½ teaspoon of salt. Add cavatappi noodles and cook for 9-10 minutes until al dente. Drain noodles and set aside in a strainer.
- Heat 4 tablespoons of butter over medium heat in a 4-quart Dutch oven until melted. Sprinkle in flour and whisk to combine. Whisk in Dijon mustard and 1 teaspoon of salt. Gradually whisk in milk. Heat for 3 minutes to thicken.
- Whisk in shredded Gruyère and cheddar cheese. Fold in noodles and pesto sauce. Turn off heat.
- Melt remaining 2 tablespoons of butter over medium heat in a skillet. Add panko bread crumbs and stir to coat. Sprinkle panko over mac and cheese and bake for 10-12 minutes, until panko is golden brown.
- Remove mac and cheese from oven and chop crispy prosciutto into bite size pieces. Sprinkle on top of mac and cheese. Serve hot.