Preheat the oven to 375°F.

Spray a 9-inch square baking dish liberally with nonstick cooking spray.

Slice the potatoes uniformly 1/8 inch thick. Mince the garlic clove.

In a medium sauce pan over medium heat, melt the butter. Once melted, add the minced garlic and sauté for 30 seconds, just until fragrant.

Add the flour to the sauce pan. Whisk to combine the batter and flour into a thick paste. Continue whisking for 1 minute, until the roux turns slightly golden and begins to smell toasty. Slowly stream the milk and heavy cream into the pan while continuing to whisk.

Cook the mixture, whisking steadily, until it begins to thicken and bubble, 4-5 minutes.

Once bubbling, turn off the heat. Add salt and black pepper. Add the grated Parmesan and whisk slowly until the cheese is melted and the sauce is smooth.

Arrange half of the potatoes in the baking dish in an even layer. Lightly season with more salt and black pepper. Pour half of the cheese sauce on top. Sprinkle with half of the shredded cheese. Repeat with the remaining potatoes slices, sauce, and shredded cheese.

Bake the scalloped potatoes on middle rack of oven until the potatoes are tender and the dish is bubbling and browned on the top, 40-45 minutes.

Check to see that potatoes are done. Remove from oven or add time as needed.

Allow the dish to cool for 10 minutes.

Garnish with chopped chives, if desired. Use a large spoon to plate the scalloped potatoes, and serve.