1-Getting started: with this cheesy au gratin potatoes recipe is as easy as turning on your oven. Begin by preheating it to 375°F and greasing a 9-inch square baking dish to avoid any sticking issues. This sets the stage for a dish that cooks evenly and comes out just right.

2-Next: carefully arrange the potato slices in 3 4 slanted rows in the dish, making sure to leave space for the sauce and onions. Add the thinly sliced onion between and on top of the potato layers for that extra burst of flavor. It’s a simple way to build depth without complicating things.

3-For the sauce: melt 3 tablespoons of salted butter over medium heat and whisk in ¼ cup of flour to form a paste it only takes about 30 seconds. Gradually add 1 ½ cups of milk while whisking, bring it to a boil, then simmer on medium-low until it thickens, around 5 minutes. Stir in 8 ounces of freshly shredded sharp Cheddar cheese, ¾ teaspoon of kosher salt, ½ teaspoon of garlic powder, and some freshly ground black pepper, then adjust seasoning as needed.

4-Pour the cheese sauce: evenly over the potatoes and onions, cover with foil, and bake for 45 minutes. After that, remove the foil and sprinkle on 2 ounces of shredded Gruyere and 2 ounces of grated Parmesan cheese. Bake uncovered for 30 to 45 minutes until the potatoes are tender and the top is golden brown, and if you like, broil for 1 2 minutes for extra crispness. Let it cool for 10 minutes, garnish with chopped chives or parsley, and serve warm. For a fun twist, try pairing it with a side like garlic butter steak and potatoes from our site for a complete meal.