Preheat oven to 400° F and place a rack in the center of the oven.
Cook pasta 3 minutes shy of al dente according to package directions. Drain, but do not rinse.
Meanwhile, while the noodles are cooking, make the breadcrumb topping and cheese sauce.
For the topping, combine the panko breadcrumbs, melted butter and 1 teaspoon truffle salt. Mix until well incorporated. Set aside.
To prepare the cheese sauce, place the milk, cheese, nutritional yeast, garlic, remaining 3 teaspoons of truffle salt, and pepper into a high-powered blender and pulse until smooth, about 30 seconds to 1 minute. Taste and adjust seasonings.
Stir together the partially cooked pasta with the cheese sauce and shaved brussels sprouts, mixing to ensure all the pasta is coated in the cheese sauce.
Transfer the Mac and cheese to a 9x13 - inch baking dish and top with the panko breadcrumbs. Cover with aluminum foil and bake in the preheated oven for 10 minutes. Remove the foil and bake an additionally 15 minutes, or until the cheese is bubbly and the breadcrumb topping is golden-brown and crispy.
Sprinkle with fresh parsley and enjoy!