Step 1: Preheat your smoker to 225-250°F (107-121°C). Prepare your desired wood chips (apple, cherry, or pecan work well).
Step 2: Cook the macaroni according to package directions until al dente. Drain well and set aside.
Step 3: In a large, heavy-bottomed pot or Dutch oven, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes, stirring constantly, until a smooth paste (roux) forms. Do not let it brown too much.
Step 4: Gradually whisk in the warmed whole milk, a little at a time, ensuring there are no lumps. Continue whisking until the sauce thickens and comes to a gentle simmer, about 5-7 minutes.
Step 5: Reduce the heat to low. Add the smoked paprika, Dijon mustard, salt, and black pepper. Stir well. Begin adding the shredded cheeses (cheddar, Gruyère, smoked Gouda) in handfuls, stirring continuously until each addition is fully melted and smooth before adding more.
Step 6: Once all the cheese is melted and the sauce is smooth and creamy, remove the pot from the heat. Add the cooked and drained macaroni to the cheese sauce, stirring gently until every piece of pasta is thoroughly coated.
Step 7: Transfer the macaroni and cheese mixture to a large, disposable aluminum pan (approx. 9x13 inches) or an oven-safe cast iron skillet. Spread evenly.
Step 8: Place the pan directly on the grates of your preheated smoker. Smoke for 1.5 to 2 hours, stirring gently every 30-45 minutes to ensure even smoke distribution and to prevent the edges from drying out. The mac and cheese should develop a beautiful golden-brown crust and have a rich, smoky aroma.
Step 9: Carefully remove the smoked mac and cheese from the smoker. Let it rest for 10-15 minutes before serving to allow the sauce to set slightly and the flavors to meld.
Step 10: Garnish with fresh chopped parsley or chives, if desired, and serve warm. Enjoy your incredible smoked mac and cheese!