Preheat the oven to 400°F (200°C). Spray at least 2-inch deep large casserole dish with cooking spray.
Cut the potatoes into 1/8-inch thin slices. (TIP: Use a mandoline slicer for even slices.) 3-4 medium russet potatoes
In a medium bowl, whisk together ½ cup of heavy cream, flour, garlic, salt, and pepper until well combined. Then stir in the remaining heavy cream, milk and cilantro.
2 tablespoons all-purpose flour, 1 tablespoon minced garlic, 1 ½ teaspoon salt, 1 ½ teaspoon ground black pepper, 1 cup heavy cream, 1 cup milk, ½ cup loosely packed cilantro
Arrange half of the potatoes in prepared baking dish. Then pour half of the cream mixture over the potatoes and sprinkle half of each cheeses in even layer.
4 oz mozzarella cheese, 4 oz Havarti cheese
Layer the remaining potato slices, pour the remaining cream mixture and sprinkle the cheeses.
Cover with foil and bake for 30 minutes.
Remove the foil and bake another 20 minutes, or until the potatoes are fork-tender. If desired, broil for about 2 minutes for beautiful golden color.
Rest for 10-15 minutes before serving.