Preheat the oven to 180°C. Butter a 23 x 33 cm baking dish and set aside.
1 tablespoon butter
Bring the chicken broth (or salted water) to a boil. Add the macaroni and cook until just shy of al dente, then drain.
2.4 liters chicken broth, 450 g elbow macaroni
In a large bowl, combine the half-and-half, heavy cream, half of the cheddar, half of the Colby Jack, all of the mozzarella, the American cheese, and the cream cheese.
240 ml half-and-half, 240 ml heavy cream, 225 g aged cheddar, 225 g Colby Jack, 225 g mozzarella, 225 g American cheese, 115 g Philadelphia-style cream cheese
Add the smoked paprika, garlic powder, onion powder, mustard powder, salt, and black pepper. Mix well, taste, and adjust the seasoning lightly if needed.
Stir in the cooked macaroni, then mix in the eggs.
2 eggs
Transfer to the baking dish and spread evenly. Sprinkle with the remaining cheddar and Colby Jack, plus a little smoked paprika if desired.
Bake for about 35 minutes, until the top is golden and bubbling, without overbaking.
Let rest for about 5 minutes, then serve hot.
Notes
Eggs are essential here: the whites help the mac & cheese set, while the yolks add richness and help prevent a grainy texture. You can substitute unsweetened evaporated milk for the half-and-half. Avoid very aged cheeses, which tend to separate as they cook.