Begin by bringing a large pot of salted water to a boil. Add elbow macaroni and cook for about 6 minutes, or until al dente. Drain the cooked macaroni and set aside.

In a large skillet over medium heat, melt the unsalted butter. Whisk in the all-purpose flour and cook for 1-2 minutes.

Gradually whisk in Guinness Draught Stout, stirring until smooth and the mixture comes to a gentle simmer.

Slowly pour in the whole milk while whisking continuously. Let the sauce simmer for about 5 minutes until it thickens slightly.

Stir in the shredded sharp Irish cheddar cheese and mozzarella, mixing until fully melted and the sauce is glossy.

Add Dijon mustard, ground mustard powder, and season with salt and black pepper. Optionally add smoked paprika.

Gently fold the cooked macaroni into the cheese sauce. Let it simmer for another 2 minutes.

In a small bowl, mix panko breadcrumbs with melted butter until evenly coated.

Transfer the mac and cheese into a greased baking dish and sprinkle the panko mixture on top. Broil for 2-3 minutes until golden brown.

Remove from the oven and let it rest for about 5 minutes before serving.