Fancy Crusted Rosemary Scalloped Potatoes

Step 1
Preheat the oven to 400 degrees F (200 degrees C). Coat an 8-inch baking dish cooking spray.

Step 2
Mix Parmesan cheese, rosemary, and garlic together in a bowl.

Step 3
Slice 3 or 4 potatoes using a mandolin on the thinnest setting. Slice remaining potatoes using a slightly thicker setting on the mandolin.

Step 4
Line the bottom of the prepared baking dish with thin potato slices, overlapping them to create a layer that is 2 to 3 slices deep. Stand remaining thin slices along the sides of the baking dish so that half an inch sticks over the rim, overlapping them to create a layer that is 4 slices deep.

Step 5
Spread 1/3 of the thicker potato slices in the baking dish. Sprinkle 1/3 of the Parmesan cheese mixture on top. Repeat once more. Arrange remaining potato slices in the baking dish. Reserve 1/3 of the Parmesan cheese mixture.

Step 6
Melt butter in a saucepan over medium heat; whisk in flour. Pour in milk; cook, occasionally stirring, until sauce thickens, 5 to 6 minutes. Stir in salt.

Step 7
Shift potato slices in a few places with a knife to create wells for the sauce to flow through. Pour sauce evenly over potato slices in the baking dish. Sprinkle remaining 1/3 of the Parmesan cheese mixture on top. Brush potato edges sticking out of the baking dish with olive oil.

Step 8
Bake in the preheated oven until potatoes are soft and edges are crusted, 1 hour to 1 hour and 15 minutes.