Fancy Crusted Rosemary Scalloped Potatoes

Preheat the oven to 400 degrees F (200 degrees C). Coat an 8-inch baking dish with cooking spray. (5 minutes)

In a bowl, thoroughly mix the Parmesan cheese, minced fresh rosemary, and minced garlic. Set aside. (5 minutes)

Using a mandolin, slice 3 or 4 potatoes on the thinnest setting for the crust. Slice the remaining potatoes on a slightly thicker setting for the filling. (15 minutes)

Line the bottom of the prepared baking dish with the thin potato slices, overlapping them to create a layer that is 2 to 3 slices deep. Stand the remaining thin slices along the sides of the baking dish, allowing about half an inch to extend over the rim. Overlap these slices to create a crust that is approximately 4 slices deep. (20 minutes)

Spread 1/3 of the thicker potato slices evenly in the baking dish. Sprinkle 1/3 of the Parmesan cheese mixture on top. Repeat this process once more, layering potatoes and cheese. Arrange the remaining potato slices in the baking dish. Reserve the final 1/3 of the Parmesan cheese mixture. (10 minutes)

In a saucepan over medium heat, melt the butter. Whisk in the all-purpose flour until smooth. Gradually pour in the whole milk, whisking continuously to prevent lumps. Cook, stirring occasionally, until the sauce thickens to a creamy consistency, approximately 5 to 6 minutes. Stir in the salt. (10 minutes)

Use a knife to gently shift the potato slices in a few places, creating small wells for the sauce to penetrate. Pour the sauce evenly over the potato slices in the baking dish. Sprinkle the reserved 1/3 of the Parmesan cheese mixture over the top. Brush the potato edges that are sticking out of the baking dish with olive oil to promote browning. (5 minutes)

Bake in the preheated oven until the potatoes are tender and the edges are beautifully crusted and golden brown, approximately 1 hour to 1 hour and 15 minutes. Let rest for 10 minutes before serving. (75 minutes)