Preheat oven at 375°. Grease the oven safe dish. Cook pasta slightly under al-dente. Drain and set aside.
Melt butter in a Dutch oven over medium heat. Whisk in flour and cook 2 minute, whisking constantly until the raw smell goes away.
Gradually whisk in milk, cook over medium heat, whisking until mixture thickens and is bubbly. Remove from heat.
Add cheeses, salt, stirring until cheese melts and sauce is smooth.
Stir in pasta and cook over medium heat, 1 minute or until thoroughly heated. Transfer into oven safe baking dish.
Mix paprika in breadcrumbs/panko. Make a layer of bread crumbs/panko on top of Mac n' cheese. Put in oven at 350 degree for about 20 minutes or until bread crumb/panko is golden brown color and it's bubbly!!
Serve immediately!