Start by boiling a large pot of salted water for the noodles. Cook elbow macaroni al dente as instructed on the box.
While noodles are cooking, melt butter in a large saucepan over medium heat.
While the butter is melting, pour whole milk into a large coffee cup. My mom always mixed it in a coffee cup, so I do too. Stir in the cornstarch with the milk. Once the butter is melted, pour in the milk/cornstarch mixture.
Turn the heat to medium-low until it starts to bubble and thicken into a creamy cheese sauce. Once you can see it thickening, add in the cheese, and slowly stir until it all melts together. Place on low heat if necessary to prevent burning.
Strain the cooked pasta and place it back in the pan, pour the cheese mixture over noodles, and stir well. Add in salt and black pepper to taste.
For a creamy baked mac version, transfer the mac and cheese into a baking dish, top with panko bread crumbs, and bake at 350 degrees F until the top is golden brown.