Preheat the oven to 350°F.
Bring a large pot of water to a rolling boil. Once boiled, add the macaroni to the pot and cook until al dente.
As the pasta cooks, make a roux. Melt the remaining butter in a large skillet over medium-high heat. Add flour and whisk for 2 minutes.
Gradually add the milk, cream, and mustard to the skillet. Season, then bring to a simmer, whisking occasionally until the sauce is slightly thickened.
Slowly add the Vertage cheese shreds and mix until fully incorporated. Next, fold in the cooked macaroni.