1. Preheat the Oven and Prepare the Dish:

1. Preheat your oven to 375°F (190°C).
2. Grease a 9×13-inch baking dish with butter or cooking spray.

2. Prepare the Cream Sauce:

1. In a medium saucepan, melt the butter over medium heat.
2. Add the minced garlic and cook for 1 minute until fragrant.
3. Stir in the flour and cook for 1-2 minutes to remove the raw flour taste, creating a roux.
4. Gradually whisk in the milk and cream, ensuring there are no lumps.
5. Add the salt, pepper, and nutmeg (if using). Cook for 3-5 minutes, stirring frequently, until the sauce thickens slightly.
6. Remove from heat and stir in 1 cup of the cheddar cheese until melted.

3. Assemble the Potatoes:

1. Arrange half of the sliced potatoes in an even layer in the prepared baking dish.
2. Pour half of the cream sauce over the potatoes, spreading it evenly.
3. Sprinkle with half of the Parmesan cheese.
4. Repeat with the remaining potatoes, cream sauce, and Parmesan cheese.
5. Top with the remaining 1/2 cup of shredded cheddar cheese.

4. Bake:

1. Cover the dish with aluminum foil and bake for 45 minutes.
2. Remove the foil and bake for an additional 20-25 minutes, or until the potatoes are tender, and the top is golden and bubbly.

5. Garnish and Serve:

1. Let the scalloped potatoes rest for 10 minutes before serving.
2. Garnish with fresh parsley, if desired, and serve warm.