• Preheat your oven to 350˚F and grease a 9×13-inch baking dish. Set it aside for later use.

To Make the Sauce

• In a large saucepan, melt the butter over medium-low heat. Add the diced onion and minced garlic, cooking until the onion becomes soft and translucent, about 3 minutes. Stir in the flour and cook for an additional 1-2 minutes, ensuring it’s well combined.
• Gradually add the milk and chicken broth mixture to the saucepan, starting with small amounts and whisking continuously. The sauce will thicken initially; keep adding the liquid slowly, whisking to maintain a smooth consistency. Once all the liquid is incorporated, raise the heat to medium and bring the mixture to a boil, still whisking. Stir in ½ teaspoon of salt and ⅛ teaspoon of pepper, allowing the sauce to boil for 1 minute before removing it from heat.

Assembly

• Layer one-third of the potato slices in the prepared baking dish, seasoning each layer with ¼ teaspoon of salt and ⅛ teaspoon of pepper. Pour one-third of the cream sauce over the potatoes. Repeat the layers, finishing with a layer of cream sauce on top. Cover the dish with foil and bake for 45 minutes.
• After 45 minutes, uncover the dish and continue baking for an additional 35-45 minutes, or until the top is golden brown and the potatoes are tender. For an extra crispy top, broil the dish for 3-4 minutes.
• Let the dish rest for at least 15 minutes before serving to allow the flavors to meld and the sauce to thicken. Enjoy your creamy, flavorful scalloped potatoes!