Begin by bringing a large pot of salted water to a rolling boil. Add the elbow macaroni and cook for about 7-8 minutes, or until just tender but still al dente. Drain the pasta and set aside.

In a medium saucepan, melt 4 tablespoons of butter over medium heat. Whisk in 4 tablespoons of flour, cooking for 1 minute to form a roux. Gradually pour in 3 cups of milk, whisking continuously until thickened, about 3-4 minutes.

Once thickened, remove from heat and stir in 2 cups of shredded cheddar cheese and ½ cup of grated Parmesan cheese until melted and smooth. Season with salt and pepper to taste.

Fold the drained macaroni into the cheese sauce until well coated.

Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish and pour the mac and cheese mixture into it, spreading evenly.

Slice the mozzarella cheese into ghost shapes and place them on top of the pasta. Press down slightly to meld with the mixture. Optionally, add black sesame seeds or peppercorns for eyes.

Bake in the oven for 20-25 minutes until the cheese is bubbly and golden.

Remove from the oven and let cool for a few minutes before serving.