Preheat the oven to 325° F (165°C). Grease a 3 qt (9×13-inch) baking dish and set aside.
Fill a large pot about three-fourths full with water, and bring to a boil over medium-high heat. Season generously with salt. When the water is boiling, add the elbow macaroni. Cook according to the package directions, subtracting 1 to 2 minutes from the suggested time. Don’t overcook because the pasta will finish cooking in the oven. Drain well and set aside.
In a medium bowl, combine the sharp cheddar cheese and raclette or Gruyère cheese. Set aside.
To the same pot over medium heat, melt the butter. Add the flour and quickly whisk. Cook for about 1 - 2 minutes, whisking frequently.
While constantly whisking, add in half of the milk. Stir until it begins to thicken, and then add the rest of the milk, all the heavy whipping cream, mustard, 1 ½ teaspoon salt, black pepper and paprika. Continue to stir and heat until the mixture is glossy and lightly thickened.
Turn off the heat and whisk in half the cheese mixture. Continuously stir for 3 - 4 minutes, or until the cheese is completely melted and the sauce is glossy.
Gently fold the cooked macaroni into the cheese mixture; mix until completely coated with the cheese. Pour half of the cheesy pasta evenly into the prepared pan. Add half the remaining cheese mixture, followed by the other half of the cheesy pasta, and finally top with the remaining cheese mixture.
Bake for 13 - 15 minutes or until bubbly and melted. The last 2 minutes, turn on the broiler and lightly brown the top to your liking. Serve immediately while hot.