Bring 5 quarts of water to a boil in a large stockpot over high heat. Add 1 tablespoon of salt.
Add the macaroni and stir. Cook for 2 minutes less than the time recommended on the package, stirring periodically to keep the pasta from sticking. Drain macaroni well and transfer to a large mixing bowl.
Meanwhile, melt 8 tablespoons (1 stick) butter into a medium saucepan over medium heat. Gradually add the flour and mustard, whisking constantly. Continue whisking for about 2 minutes, being careful that the mixture doesn't begin to brown.
Gradually whisk in the cream and whisk continuously until the mixture is smooth.
Reduce the heat to medium-low and stir in the Velveeta, one-third at a time, until all the cheese is incorporated and melted. Season to taste with salt and pepper.
Pour the cheese sauce over the pasta and stir gently with a rubber spatula or wooden spoon.
Butter a large oven proof casserole dish with remaining tablespoon of butter. Pour the macaroni and cheese evenly into the pan.
Sprinkle the cheddar cheese on top and spread the breadcrumbs evenly over the top of the macaroni and cheese. Dust lightly with paprika.
When ready to cook, start the Traeger according to grill instructions. Set the temperature to 350 degrees F and preheat, lid closed, for 10 to 15 minutes.
Bake the macaroni and cheese for 45 minutes to 1 hour, or until the mixture is hot and bubbling and the breadcrumbs are golden brown.
Turn the pan halfway through bake time. Serve hot. Enjoy!
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