1-First Step: Mise en Place and Prep Start by preheating your oven to 375 degrees F and greasing a 2-quart square baking dish with nonstick cooking spray, butter, or oil. Wash and thinly slice 6-7 medium Yukon gold potatoes into 1/8 inch rounds for even cooking. Measure out all your ingredients, like the sliced onion and cheeses, to make the process smooth and enjoyable.

2-Second Step: Build the Base In a pan over medium heat, melt 2 tablespoons of salted butter. Whisk in ¼ cup of all-purpose flour to create a base, then gradually add 1 ½ cups of unsweetened almond milk while whisking to avoid lumps. This step builds the flavorful foundation for your Cheesy Au Gratin Potatoes.

3-Third Step: Make the Cheese Sauce Bring the mixture to a simmer and cook until it thickens into a creamy consistency. Reduce the heat and stir in 8 ounces of shredded sharp cheddar cheese, along with ½ teaspoon garlic powder, ¾ teaspoon salt, and freshly ground black pepper to taste. Taste and adjust the seasoning to make sure it suits your preferences, creating a sauce that’s packed with flavor.

4-Fourth Step: Layer and Bake Arrange the sliced potatoes in three tight slanted rows in the prepared dish, tucking in the onion slices as you go. Pour the cheese sauce evenly over the potatoes to coat them fully, then cover with foil and bake for 45 minutes. After that, remove the foil, sprinkle on ½ cup Gruyere cheese and ¼ cup grated Parmesan cheese, and bake uncovered for 30-45 minutes more until the potatoes are fork-tender and the top is golden.

5-Fifth Step: Rest and Serve Once baked, let the dish rest for a few minutes to set, then garnish with fresh chopped parsley. For tips on enhancing flavor, such as adding cooked bacon, remember that slicing potatoes evenly with a mandoline helps for uniform cooking. This method ensures your Cheesy Au Gratin Potatoes turn out perfectly every time, with a total prep time of 30 minutes and cook time of 1 hour 15 minutes.