Prepare a 9"x13" baking dish with nonstick cooking spray or butter.
Bring a large saucepan of salted water to a boil over high heat. Add the pasta and cook, stirring occasionally, for about 2 minutes less than package instructions. Drain the pasta and put in large mixing bowl. While pasta is still warm, stir in 1 tablespoon White Truffle Flavored Butter. Use up to 2 tablespoons for more truffle flavor.
While pasta is cooking, melt salted butter in a saucepan over medium-high heat. Add flour and mustard. Cook, stirring well, until no visible flour remains, about 1 minute. Whisk in the half & half and milk and cook until bubbling. Turn heat down to low and cook 4-5 minutes or until smooth. Remove from heat and add pepper, to taste. Add 2 cups shredded white cheddar and stir until cheese is melted and sauce looks creamy, 1-2 minutes.
Pour the cheese sauce onto the pasta and mix well. Transfer to the baking dish and top with the remaining 1 cup cheese. Melt 1 tablespoon White Truffle Flavored Butter in a small bowl. Mix in panko breadcrumbs and pour over pasta. Bake 25 minutes or until cheese is lightly browned and sauce is bubbling. Broil for 1 minute to brown panko and then remove from oven.