Cook the pasta. Boil the macaroni for 2 minutes less than the box says, so it is still firm. Drain it and set it aside.
Make the roux and sauce. In a large pot over medium heat, melt the butter. Stir in the flour and keep stirring for about a minute; it will look like a paste. Slowly pour in the milk while whisking, and keep whisking until the sauce thickens, about 5 minutes.
Melt in the cheese. Take the pot off the burner. Stir in the shredded cheddar, gouda, and cream cheese until everything is melted and smooth. Stir in the mustard powder, salt, and pepper.
Add the eggs slowly. Crack the eggs into a small bowl and whisk. Spoon 2-3 spoonfuls of the hot cheese sauce into the eggs and stir. Add another spoonful or two, stirring as you go. Pour the warmed egg mixture into the large pot and stir it in. Warming the eggs gradually keeps them from scrambling in the hot cheese sauce.
Mix in the macaroni. Add the cooked macaroni to the pot and stir until every noodle is coated.
Pack the pan. Line a 9x13 baking dish with parchment paper. Add the mac and cheese and press it down flat and firm. Lay another sheet of parchment on top and set something heavy on it, such as a second baking dish with a few cans.
Chill overnight. Refrigerate at least 4 hours; overnight (12-48 hours) is best. The cold, packed slab is what lets you cut cubes that survive the smoker. About 18 hours is ideal.