Ingredients:
- 3 lbs Russet or Yukon Gold Potatoes (Peeled and uniformly sliced 1/8 inch thick)
- 3 Tbsp Unsalted Butter
- 3 Tbsp All-Purpose Flour
- 2 cups Whole Milk (Warmed slightly)
- 1 cup Heavy Cream (Double Cream)
- 1 cup Freshly Grated Gruyère Cheese
- 1/2 cup Freshly Grated Parmesan Cheese
- 2 cloves Garlic (Minced very finely)
- 1 tsp Kosher Salt (or to taste)
- 1/2 tsp Freshly Ground Black Pepper
- Pinch of Nutmeg
- 1 tsp Unsalted Butter (for greasing)
- 1 tsp Fresh Thyme Leaves (Optional)
Instructions:
- Preheat oven to 375°F (190°C). Lightly grease a 2-quart casserole/baking dish with 1 tsp of butter. Slice potatoes uniformly thin (about 1/8 inch thick).
- Make the base: In a medium saucepan over medium heat, melt the 3 Tbsp of butter. Whisk in the flour and cook for 1 minute to create a roux.
- Build the béchamel: Slowly whisk in the warm milk until smooth. Continue whisking constantly until the sauce thickens enough to coat the back of a spoon (about 5-7 minutes).
- Finish the cheese sauce: Remove the pan from the heat. Stir in the heavy cream, minced garlic, salt, pepper, nutmeg, Gruyère, and Parmesan until the cheese is fully melted and the sauce is smooth.
- Layer the dish: Arrange one-third of the sliced potatoes in an even layer in the prepared dish. Sprinkle lightly with one-third of the fresh thyme leaves, if using.
- Add sauce and repeat: Pour one-third of the cheese sauce evenly over the potatoes. Repeat the layering process two more times (Potatoes, Thyme, Sauce), ensuring the top layer of potatoes is fully submerged in the sauce.
- The Initial Bake (Covered): Cover the baking dish tightly with foil and bake for 35 minutes.
- The Final Bake (Uncovered): Remove the foil. Return to the oven and bake for an additional 25–40 minutes, until the top is bubbling, beautifully browned, and a knife inserted meets no resistance.
- Rest & Serve: Let the scalloped potatoes rest on the counter for at least 10 minutes before slicing and serving to allow the sauce to set.