Preheat oven to 350 degrees F.
Bring water to a boil in a large pan, making sure to salt it generously. Once boiling, add in pasta and cook until Al dente, according to the box instructions.
While the pasta is cooking, add the butter to a medium saucepan. Once the butter has melted, add in the garlic and cook until fragrant, about 1 minute. Whisk in flour and until it is completely absorbed. Slowly whisk in the heavy cream, until smooth. Add in the nutmeg, paprika, salt and pepper and allow to simmer for 2-3 minutes.
Whisk in all the cheeses a little at a time until completely melted, continue to simmer for a couple minutes, stirring occasionally. Add the Dijon mustard and additional salt and pepper to taste. If the cheese sauce is too thick, thin it out with a little more heavy whipping cream.
Once pasta has finished cooking, strain it and put it back in the pan. Then pour the cheese sauce over it, stir until incorporated. Transfer the mac n cheese to a greased, medium-sized casserole dish.
Add both breadcrumbs and 2 tablespoons of butter to a medium skillet and toast until breadcrumbs are golden brown. Remove from heat and add the Parmesan cheese and salt. Sprinkle the breadcrumbs over the top of the mac and cheese.
Bake for 20 minutes and serve immediately, garnish with the fresh parsley.