Ingredients
- 2 pounds of Russet potatoes, peeled and thinly sliced (about 1/8" thick)
- 1¼ cups heavy cream (or half-and-half if you prefer it lighter)
- 1 cup grated Gruyère cheese
- 2 cloves garlic, smashed or minced
- 2 tablespoons butter (plus a little extra for greasing the baking dish)
- 1 teaspoon kosher salt
- ½ teaspoon freshly ground black pepper
- 2-3 fresh thyme sprigs or a pinch of dried thyme
Method
Preheat the Oven
- Set your oven to 375°F (190°C).
Prepare the Potatoes
- Peel the potatoes and slice them thinly (about 1/8" thick) using a sharp knife or mandoline. Uniform slices help them cook evenly.
Warm the Cream Mixture
- In a saucepan over medium-low heat, melt the 2 tablespoons of butter.
- Add the garlic (and thyme, if using) and let it gently sizzle for about 1 minute, being careful not to brown the garlic.
- Pour in the heavy cream, then stir in the salt and pepper. Warm the mixture gently until you see small bubbles forming around the edges (you don't need a full boil). Turn off the heat.
Assemble the Gratin
- Lightly butter the casserole dish.
- Layer half of the sliced potatoes, overlapping them slightly, and sprinkle about half of your grated cheese on top (if you're using thyme sprigs, you could tuck a few in between layers).
- Arrange the remaining potato slices on top.
- Carefully pour the warm cream mixture over the potatoes, letting it seep between the layers.
- Top with the rest of the grated cheese.
Bake the Gratin
- Cover the dish with foil and place it on a middle rack in the preheated oven.
- Bake covered for about 25 minutes, then remove the foil to allow the top to brown.
- Continue baking for another 15-20 minutes, or until the potatoes are tender when pierced with a knife and the top is golden brown.
Rest and Serve
- Let the gratin rest for 5-10 minutes before serving. This helps the cream set and makes it easier to slice or spoon out neat portions.