Preheat the oven to 325 degrees Fahrenheit. Lightly spray a 2-quart casserole dish with nonstick cooking spray and set aside.
Melt 2 tablespoons unsalted butter in a medium saucepan over medium heat. Whisk in 2 tablespoons all-purpose flour, 1 teaspoon salt, and ½ teaspoon ground black pepper.
Slowly whisk in 2 cup heavy whipping cream and continue to whisk for about 2 minutes, until it starts to thicken. Reduce the heat the low and whisk in ¼ cup grated parmesan cheese until melted. Remove from the heat and set aside.
Arrange half of the 2 pounds peeled and sliced russet potatoes evenly over the bottom of the prepared casserole dish. Add half of the sauce over the potatoes, followed by half of the 1 cup shredded mozzarella cheese.
Layer the remaining potatoes on top, followed by the remaining mozzarella and ¼ cup grated parmesan cheese.
Cover with foil and bake for 40 minutes. Remove the foil and bake for an additional 25-30 minutes until the potatoes are fork-tender and the cheese is browned on top. Garnish with chopped chives and serve.
Video
Notes
Updated Post on October 21, 2020Originally Posted on March 23, 2019