Bring a large pot of well-salted water to a rolling boil. Add the elbow macaroni and cook for 20 minutes. Although this is considerably longer than standard pasta cooking time, the macaroni should become exceptionally tender for this recipe.

Drain the cooked pasta thoroughly and reserve it while preparing the cheese mixture.

While the macaroni cooks, place the butter in a large pot over medium heat and allow it to melt completely.

Whisk in the all-purpose flour, salt, and paprika until the mixture becomes uniformly smooth. Continue whisking for approximately 1 minute, taking care not to let the roux develop any brown color.

Add the whole milk to the roux gradually, incorporating a small amount at a time and whisking thoroughly after each addition. This gradual process helps maintain a lump-free consistency.

After all of the milk has been incorporated, continue whisking over medium heat for another 1–2 minutes, or until the mixture visibly thickens.

Place the egg yolk in a small bowl and whisk it briefly. Slowly whisk a spoonful of the hot milk mixture into the yolk to gently raise its temperature.

Return the tempered yolk mixture to the pot and whisk until completely blended into the sauce.

Lower the heat to low. Gradually add the torn American cheese, the 8 ounces of grated extra-sharp cheddar designated for the sauce, and the entire cup of shredded Italian-blend cheese.

Stir continuously over low heat until each cheese has fully melted and the sauce develops a smooth, creamy consistency.

Add the thoroughly drained macaroni to the finished cheese sauce.

Fold and stir gently until every piece of pasta is evenly covered with the creamy cheese mixture.

Transfer the coated macaroni into a 9×13-inch baking dish and spread it into an even layer.

Distribute the remaining 8 ounces of grated extra-sharp cheddar evenly across the surface.

Place the baking dish beneath the oven broiler and cook only until the cheese topping becomes bubbly and lightly browned. Monitor it closely because the cheese can progress from browned to burned very quickly. Rotate the baking dish when necessary to encourage even coloring.

Remove the macaroni and cheese from the oven immediately after the topping reaches a golden-brown finish.

Allow the dish to cool briefly before serving it hot.