Preheat your oven to 350°F (175°C) and coat a 9×13-inch baking dish with nonstick spray. Meanwhile, bring a large pot of water to a rolling boil. Add kosher salt generously to the water, then add the elbow macaroni (or shell pasta). Cook according to the package directions until al dente. Once done, drain the pasta and set aside. I always salt the pasta water generously—it brings so much flavor to the noodles.
In a large Dutch oven or heavy-bottomed pot, heat the unsalted butter over medium-low heat until melted. Add the all-purpose flour and whisk together to form a roux, stirring constantly until the flour disappears and the mixture is smooth (about 1-2 minutes).
Gradually pour in the heavy cream and whole milk, whisking continuously to avoid lumps. Allow the mixture to come to a slight boil and thicken. Stir in the smoked paprika, white pepper, dry mustard, garlic powder, ground nutmeg, and kosher salt to taste. Just when it thickens, add 8 oz of grated smoked gouda cheese and all of the extra sharp white cheddar cheese. Whisk until the cheese melts completely and the sauce is creamy. Turn off the heat at this point. I like to adjust the salt at this stage, tasting the sauce to make sure it’s perfectly seasoned.
Add the cooked and drained pasta (from Step 1) directly into the cheese sauce (from Step 3). Stir thoroughly to make sure every noodle is coated in the rich, cheesy sauce.
Transfer the cheesy pasta mixture into the prepared baking dish. Evenly sprinkle the remaining 8 ounces of grated smoked gouda cheese over the top, covering the surface completely. Bake the dish at 350°F for 25-30 minutes, or until the top is golden and bubbly throughout.
Allow the baked mac and cheese to cool for about 15 minutes before serving so the sauce sets. Before serving, garnish with crumbled bacon if you’d like an extra layer of flavor and texture. I find that letting it cool slightly makes the slices hold together better and taste even richer.