Step 1: Preheat the Oven
- Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter and set aside.
Step 2: Prepare the Potatoes
- Slice the potatoes: Using a mandolin or sharp knife, slice the potatoes into thin rounds (about 1/8 inch thick). Try to keep them uniform for even cooking.
Step 3: Make the Cheese Sauce
- Heat the cream and milk: In a saucepan over medium heat, combine the heavy cream, milk, and minced garlic. Heat until warm but not boiling.
- Add the cheese: Stir in 1 ½ cups of the shredded Gruyère and ½ cup of the Parmesan cheese. Stir constantly until the cheese melts into a smooth sauce. Season with salt, pepper, and thyme (if using). Remove from heat.
Step 4: Assemble the Gratin
- Layer the potatoes: Arrange a layer of potato slices in the greased baking dish, slightly overlapping them.
- Pour cheese sauce: Pour a portion of the cheese sauce over the potatoes, spreading it evenly to cover them.
- Repeat layers: Continue layering the potatoes and pouring the sauce until all the ingredients are used, finishing with a layer of sauce on top.
Step 5: Add the Topping
- Top with remaining cheese: Sprinkle the remaining ½ cup of Gruyère and Parmesan on top of the assembled gratin.
- Cover: Cover the dish loosely with foil.
Step 6: Bake the Gratin
- Bake covered: Place the dish in the oven and bake for 45 minutes, until the potatoes are tender.
- Uncover and finish: Remove the foil and bake for another 15-20 minutes, or until the top is golden brown and bubbly.
Step 7: Serve
- Let it rest: Allow the gratin to cool for 10 minutes before serving. This helps the layers set.
- Garnish: Sprinkle with fresh parsley and serve warm.
Tips:
- Cheese Variations: Gruyère gives a nutty flavor, but you can substitute with sharp cheddar, mozzarella, or Swiss cheese if preferred.
- Uniform Slices: A mandolin slicer will ensure even potato slices, leading to consistent cooking.
- Make-Ahead: You can assemble the gratin a day ahead, refrigerate it, and bake when ready. Add an extra 10 minutes to the baking time if starting from cold.
Conclusion:
This Cheesy Potato Gratin is the ultimate combination of tender potatoes, rich cream, and gooey cheese. Whether you’re making it as a side dish or the star of the meal, it’s sure to be a crowd-pleaser that will have everyone asking for seconds!