Ingredients

• cooking spray
• 1.5 cups grated Parmesan cheese
• 2 tablespoons minced fresh rosemary
• 2 cloves garlic , minced
• 3.5 pounds red potatoes
• 3 tablespoons butter
• 3 tablespoons all-purpose flour
• 2 cups whole milk
• 0.5 teaspoons salt
• 1 teaspoon olive oil

Instructions

1. 1 Preheat the oven to 400 degrees F (200 degrees C). Coat an 8-inch baking dish cooking spray.
2. 2 Mix Parmesan cheese, rosemary, and garlic together in a bowl.
3. 3 Slice 3 or 4 potatoes using a mandolin on the thinnest setting. Slice remaining potatoes using a slightly thicker setting on the mandolin.
4. 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.
5. 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.
6. 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.
7. 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.
8. 8 Bake in the preheated oven until potatoes are soft and edges are crusted, 1 hour to 1 hour and 15 minutes.

Nutrition per serving