Bring a large pot of salted water to a boil and add the elbow macaroni. Cook until just tender, about 7-8 minutes. Drain and set aside.

In a medium pan, melt the butter over medium heat. Whisk in the flour for about 1 minute until bubbly, creating a roux.

Gradually pour in the milk, whisking constantly to prevent lumps. Cook for 3-4 minutes until the mixture thickens and bubbles gently.

Turn off the heat and stir in the shredded cheddar and grated Parmesan until creamy and smooth. Season with salt and pepper to taste.

Gently fold the drained macaroni into the cheese sauce, ensuring each piece is well coated.

Grease a baking dish with olive oil or butter. Pour the mac and cheese into the dish, smoothing the top with a spatula.

Cut ghost shapes out of the mozzarella cheese and place them on top, pressing gently to secure. Add sesame seeds or peppercorns for little eyes.

Place the dish in a preheated oven at 375°F and bake uncovered for 20-25 minutes, or until the top is golden and bubbly.

Allow the dish to cool for a few minutes before serving.