Preheat oven to 350. Prepare a 9x13-inch baking dish with 2 tablespoons butter.
In a heavy saucepan, whisk in cream, half-and-half and 4 tablespoons butter over medium-low heat. Add black pepper, red pepper flakes, nutmeg, and mustard, and whisk in flour. Cook the mixture about 2 minutes, until there are no more flour lumps. The mixture should not be bubbling. If so, reduce heat.
Whisk in the cheddar, manchego, and Gruyere. Keep cheese sauce on low heat until ready for the baking dish.
Using a stockpot or Dutch oven, bring 8 cups of water to a boil. Sprinkle in salt. Put in the pasta and cook for about 8 minutes. The macaroni should not be mushy. Drain and transfer to prepared baking dish.
Mix the eggs well into the pasta. Next, pour cheese sauce over macaroni and stir well. Sprinkle paprika on top of macaroni and cheese.
Bake for 40 minutes, until you have a golden crust.
Let cool for 10 minutes before serving.
When cooking the macaroni, please don't overcook it (al dente). It will be fully cooked as a finished dished in the oven.