
Preheat the smoker. Set your favorite smoker (or grill with two-zone heat) up at around 225 degrees F with a mild wood like alder or a fruit wood.
Cook the pasta. Bring a large pot of salted water to a boil. Cook 1 pound medium shell noodles for 8 to 9 minutes until just al dente. Drain and set aside.
Cook the poblanos and garlic. Melt ½ cup salted butter in a 14-inch cast iron skillet over medium heat. Add 2 poblano peppers, stemmed, seeded, and finely diced and cook for 3 to 4 minutes until softened and fragrant. Add 4 cloves grated garlic to the skillet and cook for 1 to 2 minutes, or until fragrant.
Make the cheese sauce. To the peppers and garlic, stir in 1 Tablespoon ground mustard powder, then add ⅓ cup all-purpose flour. Stir well until no lumps remain. Slowly pour in 2 cups half and half, stirring constantly. For a saucier mac and cheese, add an extra ½ cup. Add 4 ounces softened cream cheese and stir until the sauce is smooth and creamy. Add 3 cups extra sharp white cheddar and 1 ½ cups mozzarella, and stir until fully melted and silky.
Add the pasta. Pour in the drained pasta and stir gently until the sauce fully coats all of the noodles.
Make the panko topping. In a small bowl, combine 1 cup panko breadcrumbs, ⅓ cup melted butter, and 1 Tablespoon Fiesta Rub. Stir to combine, then sprinkle evenly over the top of the mac and cheese.
Smoke the mac and cheese. Transfer the skillet to a smoker preheated to 225 degrees F. Smoke for 20 to 30 minutes. For a light smoke and crispy golden topping, or up to 1 hour for a heavier smoke and casserole-style texture.
Serve and enjoy. When your mac is smoked to your preference, remove the skillet to cool for a few minutes, then serve with your favorite smoked meats, some crusty bread, or any other sides you love with mac and cheese!