1. Heat the oven to 375°F (190°C) and place a rack in the center. Lightly butter a 9×13-inch (3-quart) baking dish using 1 tablespoon of the melted butter.

2. In a large bowl or pitcher, whisk together the whole milk, chicken broth, heavy cream, and all-purpose flour until completely smooth with no lumps.

3. Whisk in the kosher salt, black pepper, Dijon mustard, garlic powder, onion powder, and smoked paprika until evenly combined.

4. Add the uncooked elbow macaroni, 3 cups of the shredded sharp cheddar, the shredded mozzarella, 1/4 cup of the grated Parmesan, and the remaining 3 tablespoons melted butter. Stir until the pasta is evenly coated and the cheese is well distributed.

5. Pour the mixture into the prepared baking dish, scraping out all the cheese and sauce. Use a spoon or spatula to press the pasta down so it is mostly submerged in the liquid. Cover the dish tightly with foil.

6. Bake for 35–40 minutes, until the pasta is just tender when you bite or poke a piece with a fork and the sauce has thickened but still looks a little loose.

7. Carefully remove the foil, stir the mac and cheese to redistribute the sauce, and smooth the top. Sprinkle the remaining 1 cup shredded cheddar and 1/4 cup grated Parmesan evenly over the surface.

8. Return the dish to the oven uncovered and bake for 10–15 minutes more, until the top is deeply golden and bubbling. For extra browning, broil for 1–2 minutes, watching very closely.

9. Let the mac and cheese rest for 10 minutes so the sauce can thicken and cling to the pasta, then sprinkle with the chopped parsley or thyme before serving.