Preheat oven to 350 degrees (F).
For your cream sauce, melt butter in medium saucepan, add onion and garlic, and heat over low heat until onion is softened, about five minutes. Add flour and whisk to combine until smooth.
Combine your milk and broth and add to saucepan a little at a time, whisking to thicken. Keep adding the liquid while still whisking until all combined and thick and creamy. Add salt and pepper to taste. turn off heat. Add shredded cheese, stirring to combine (if using).
Grease a 9x13-inch baking pan and place 1/3 of the thinly sliced potatoes in the bottom of the pan and pour 1/3 of cream sauce over potatoes.
Repeat layers ending with the sauce. Cover with foil, bake for 50 minutes or until tender. Broil for a few minutes to brown top.
Rest for 15 to 20 minutes before serving. Enjoy!
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