Dad’s Creamy Cheesy Au Gratin Potatoes

Instructions

1. 1

   Preheat the oven to 375°F and spray a 9-inch square baking dish with cooking spray.

2. 2

   Place the sliced potatoes in the prepared dish in three or four rows, making sure they are slightly slanted.

3. 3

   Add the onion slices in between and on top of the potatoes.

4. 4

   In a medium pot, melt the butter over medium heat, then whisk in the flour and cook until a paste forms, about 30 seconds.

5. 5

   Slowly stream in the milk while whisking to smooth out lumps, then bring the mixture to a boil.

6. 6

   Reduce heat to medium-low and simmer, stirring occasionally, until the sauce thickens, about 5 minutes.

7. 7

   Remove from heat and stir in the Cheddar, salt, garlic powder, and pepper.

8. 8

   Pour the sauce evenly over the potatoes and onions, then cover the pan with foil and bake for 45 minutes.

9. 9

   Remove the foil and sprinkle the Gruyere and Parmesan over the top.

10. 10

    Bake uncovered until the potatoes are tender and the top is golden brown, about 30 to 45 minutes.

11. 11

    Let cool for 10 minutes, then garnish with chives and serve warm.