Creamy Scalloped Potatoes

1. Preheat oven to 375 degrees.
2. Peel and slice potatoes using a food processor or mandoline to ensure uniform thickness.
3. Make a roux by melting butter and whisking in flour. Cook for a couple of minutes and whisk in warm milk. Add garlic salt, pepper, and parmesan cheese.
4. Grease a 3-quart cooking dish. Layer potatoes, sauce, and a little salt. Repeat layers, ending with sauce. Top with a little more parmesan.
5. Bake, covered with foil, for 45 minutes. Remove foil and continue cooking for 30-45 minutes or till potatoes are tender and the top is nicely browned. Raise the oven temperature at the end of the cooking time if necessary to achieve browning.