Preheat the oven to 350 degrees and grease a 9 x 13 inch casserole dish.
Bring a large pot of salted water to a boil. Boil the noodles according to package directions, then drain and return to the pot. If the sauce is not quite done, toss the pasta with a little olive oil to keep it from sticking.
Meanwhile, make the cheese sauce. In a large sauce pan, melt the butter over medium heat. Add the flour and whisk constantly, cooking for 1-2 minutes, until smooth and thick.
Slowly drizzle in the milk and half and half, about a ½ cup at a time, whisking constantly. The mixture will be thick and gloppy at first, but will eventually thin and smooth out. Bring the mixture to a gentle simmer. Cook 3-4 minutes, stirring continuously, making sure to scrape the bottom and sides of the pan well. When the mixture is thickened enough to coat the back of a spoon, turn the heat all the way down to low.
Whisk in the salt, mustard powder, garlic, cayenne, pepper, and paprika.
Stir in all of the blue cheese, and most of the cheddar, fontina and American, reserving about 1 cup total. Continue stirring until all the cheese is melted.
Pour the noodles into the greased pan, followed by the cheese sauce. Stir well. Top with the reserved cheese. Bake, uncovered, for 20-22 minutes, or until the sauce is bubbling and cheese is very melty. Serve.