Scalloped Potatoes with Heavy Cream

Preheat oven to 350 degrees Fahrenheit. Lightly grease a 2 quart casserole dish with butter or oil.
Make the cheese sauce. Melt the butter in a small saucepan over medium heat. Once it’s sizzling, add the flour and stir with a fork to make a paste, then cook for another minute.
Slowly whisk in the heavy cream, making sure the sauce is smooth and fully incorporated, then add the thyme, garlic, salt and pepper, and bring to a light simmer, about 3 minutes.
Once the cream mixture is simmering, stir in ½ cup of parmesan and ¾ cup of cheddar, so it melts into the cream and is smooth, about 30 seconds. Once mixed, remove pan from heat.
Wash and peel the potatoes. Use a mandoline, sharp knife, or food processor to thinly slice your potatoes to 1/16 inch thickness (about the thickness of a nickel). Transfer all of the slices into a large mixing bowl.
Grease the casserole dish. Layer the sliced potatoes in the dish in an even layer, then top with some of the cheese sauce.
Repeat with three more layers of potatoes and cheese sauce.
Sprinkle the remaining ¼ cup of parmesan and ¼ cup of cheddar on top.
Bake in the preheated oven for 65 to 75 minutes uncovered, until potatoes are tender with a nice crusty top.
Let it cool for at least 20 minutes before slicing and serving.