Recipe Prep: Preheat oven to 350°F. Lightly grease an 8×8 pan (or an 8-inch round baking dish) with butter or nonstick cooking spray.

1. Arrange the potato slices inside the pan, seasoning with salt and pepper between the layers so our gruyere potatoes au gratin doesn’t taste bland. You can stand up the slices, slightly fanning them out, or toss them into the pan and spread them out. Cover the dish with a damp cloth to help prevent oxidation (potatoes turning a purplish grey color).
2. Melt the butter in a large saucepan over medium heat. Add garlic and cook for 1 minute.  Sprinkle flour into the pan. Season with herbes de Provence, onion powder, and salt and pepper. Continuously whisk until a roux forms. Then cook the roux for 1 minute.  Slowly add the milk, whisking constantly. Continue whisking until no large lumps remain. Taste the bechamel. Add more seasoning if needed.
3. Cook the sauce (about 3 minutes) until it has thickened enough to coat the back of a spoon. Stir in 1/2 cup gruyere, 1/2 cup cheddar cheese, and nutmeg (or paprika), if using. Keep stirring until the cheese has completely melted. Taste the bechamel. If needed, add more seasoning to taste.
4. Pour the bechamel over the potatoes. If the potatoes are standing upright, spread the sauce between the slices and along the edges of the pan. The sauce should be distributed throughout the dish, not just sitting on top of the potatoes. If the potatoes were tossed into the dish, then gently stir to incorporate the sauce. 
5. Cover the top of the dish with foil to protect the casserole from over-browning in the oven. Bake for 50 minutes. Remove the pan from the oven. Sprinkle the remaining gruyere and cheddar over the top, as well as the cracker crumbs. 
6. Return the casserole to the oven and bake for an additional 40 to 50 minutes, or until the top is golden brown and the potatoes are fork tender. Garnish the gruyere potatoes al gratin with fresh thyme, Italian parsley or chives.