INSTRUCTIONS:

1st Step

Heat the oven to 350 degrees Fahrenheit (175 degrees Celsius). Butter or spray a 9×13-inch baking dish with cooking spray.

2nd Step

Melt the butter in a medium saucepan over medium heat. Cook for approximately 1 minute, or until the garlic is aromatic. To make a roux, stir in the flour. Cook for 2-3 minutes, or until the color becomes light golden.

3rd Step

Whisk in the heavy cream and milk gradually, whisking frequently to avoid lumps from developing. Cook for 5-7 minutes, or until the sauce thickens and coats the back of a spoon.

4th Step

Stir in the shredded cheddar and grated Parmesan cheese until the cheese is completely melted and the sauce is smooth. Season with salt, black pepper, and dried thyme (if using) to taste. Season with salt and pepper to taste.

5th Step

In the oiled baking dish, arrange a layer of thinly sliced potatoes, gently overlapping each slice. Pour a portion of the creamy sauce over the potatoes, making sure they’re well coated.

6th Step

Repeat the stacking of potatoes and sauce until all of the potatoes have been used up. Don’t forget to top with a layer of sauce.