1. Preheat oven to 375 degrees F.
2. Peel potatoes and hold them in a bowl of water.

Make your Béchamel Cheese Sauce

1. In a medium saucepan, melt butter over medium heat, then add garlic and cook for 30 seconds or until fragrant. Stir constantly so the garlic doesn't burn.
2. Add in flour and continuously stirring cook for about 30 secs. 
3. Whisk in milk and heavy cream gradually, keeping at a low simmer, about 1/2 cup at a time.  Slow down if you lose your simmer. 
4. Add 1 tsp of sea salt and 1/4 tsp black pepper and hot sauce if you're adding it.
5. Once sauce is thickened to about the consistency of heavy cream to buttermilk, turn burner down to low and whisk in your shredded gruyere cheese.
6. Once fully melted, turn off burner and remove from heat.  Let sit while you start slicing and building the Au Gratin Potatoes.

Build your Au Gratin Dish

1. Slice a few potatoes at a time or all if you can work fast and add them to your greased baking dish, in a "scalloped" fashion, overlapping about 1/3 of the way till you cover the bottom of the baking dish.
2. Grind or sprinkle just a little salt and pepper to the potato layer.
3. Spoon on a spread out about 1/3 of the béchamel sauce onto the potatoes
4. Scatter about 1/3 of the shredded cheese atop the sauce and then make 2 more layers of potatoes, salt & pepper, sauce & cheese.
5. Your top layer (the 3rd one will have the last of the scattered shredded cheese on top.
6. Bake the Au Gratin for 1 hr at 375 F.  It should be nice and golden on top and bubbling.  You can test the tenderness with a sharp knife if you like before removing it from the oven.
7. Let the potatoes sit for at least 10 minutes and then you can serve it by slicing it into squares.