1-Start by preheating your oven to 350°F and greasing a casserole dish, which takes about 25 minutes of prep time. This sets the stage for a dish that bakes for around 1 hour and 20 minutes, plus 15 minutes to rest, totaling two hours of effort for a rewarding meal.

2-First, make the sauce by melting ¼ cup salted butter over medium-low heat in a pan. Add 1 large yellow onion, diced, and 2 cloves garlic, minced; cook until softened, about 3-4 minutes, then stir in ¼ cup all-purpose flour and cook for 2 more minutes. This base adds rich flavor to your scalloped potatoes.

3-Next, gradually whisk in 2 cups milk and 1 cup chicken broth until smooth, then bring it to a boil while adding ½ teaspoon salt and ⅛ teaspoon black pepper. Let it boil for 1 minute to thicken. Layer one-third of the 3 pounds of sliced Yukon gold or red potatoes in the dish, seasoning with ¼ teaspoon salt and ⅛ teaspoon pepper before pouring one-third of the sauce over them.

4-Repeat the layers twice more, ending with sauce on top, then cover tightly with foil and bake for 45 minutes. Uncover and bake an additional 35-45 minutes until golden and tender. For a nicer finish, broil for 3-4 minutes, and let it rest for at least 20 minutes before serving to allow the flavors to settle.