Cook the macaroni in a large pot of salted, boiling water until al dente. Drain immediately and rinse with cold water to stop the cooking process. Set aside.
In a large pot or Dutch oven over medium heat, melt the butter. Whisk in the flour and cook for 1 minute, whisking constantly.
Gradually whisk in the whole milk and heavy cream until the mixture is smooth. Bring to a gentle simmer and cook until the sauce has thickened slightly.
Reduce the heat to low. Stir in the softened cream cheese until it has completely melted.
Add the grated cheddar, smoked Gouda, and Parmesan cheeses in batches, stirring until the sauce is smooth and velvety. Stir in the mustard powder, salt, and pepper.
Gently fold the cooked pasta into the cheese sauce until well combined.
Pour the macaroni and cheese into a 9x13 inch smoker-safe pan (a cast-iron skillet or disposable aluminum pan works well).
If using the topping, mix the panko breadcrumbs with the melted butter and sprinkle evenly over the mac and cheese.
Preheat your smoker to 225°F-250°F using a mild wood like apple or cherry.
Place the pan in the smoker and cook for 1 to 2 hours, or until the mac and cheese is hot, bubbly, and golden brown on top. Let rest for a few minutes before serving.