Preparing cheesy scalloped potatoes is a simple process that yields delicious results. Follow these steps to create this incredible dish:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Prep Baking Dish: Grease a 3-quart baking dish with butter or cooking spray.
3. Sauté Onions and Garlic: In a skillet, melt 2 tablespoons of butter over medium heat. Add the chopped onions and cook until translucent, about 5 minutes. Stir in the minced garlic and sauté for an additional 1-2 minutes, until fragrant.
4. Layer Potatoes: Begin layering the sliced potatoes in the greased baking dish. Spread half of the potatoes in an even layer, followed by half of the sautéed onions and garlic. Sprinkle with salt, pepper, and half of the cheddar cheese.
5. Repeat Layers: Add another layer of potatoes, seasoned with salt and pepper, followed by the remaining onions and garlic. Finish with the remaining cheddar cheese and Parmesan cheese.
6. Prepare Cream Mixture: In a saucepan, combine heavy cream, remaining butter, salt, and pepper. Heat over low until melted and combined.
7. Pour Cream: Carefully pour the cream mixture over the layered potatoes, ensuring even distribution.
8. Cover & Bake: Cover the baking dish with aluminum foil and bake in the preheated oven for 40 minutes.
9. Uncover & Brown: After 40 minutes, remove the foil and bake for an additional 10-20 minutes, until the potatoes are tender and the top is golden brown and bubbly.
10. Rest: Once cooked, remove the dish from the oven and let it rest for 10-15 minutes before serving. This resting period helps the dish set and enhances flavor.

By following these steps closely, you’ll be rewarded with a beautiful, creamy dish that will delight your guests.