Equipment
Ingredients
Vegetables
- 1000 g yukon gold potatoes, peeled
- 2 garlic, minced
Custard Base
- 400 ml whole milk, room temperature
- 3 eggs, room temperature
Cheese and Seasonings
- 150 g gruyere cheese, freshly grated
- 20 g unsalted butter, softened
- 8 g kosher salt, fine
- 2 g black pepper, freshly ground
- 1 g nutmeg, freshly grated
Nutrition (per serving)
Method
Preheat your oven to 190°C (375°F).
Grease the inside of your gratin dish thoroughly with half of the softened unsalted butter, then rub the greased surface with half of the minced garlic to season the dish.
Slice the peeled potatoes evenly to 3mm thickness using a mandoline slicer. Do not wash or rinse the potatoes after slicing, as the natural starches are needed to thicken the custard.
In a mixing bowl, vigorously whisk together the whole milk, eggs, the remaining minced garlic, kosher salt, black pepper, and nutmeg until the liquid is completely homogeneous.
Layer half of the potato slices in the prepared gratin dish, arranging them in overlapping, shingled rows to create an even foundation.
Sprinkle half of the grated Gruyere cheese evenly over the first layer of potatoes.
Arrange the remaining potato slices in the same overlapping shingled pattern on top of the cheese layer.
Slowly pour the milk and egg custard mixture over the top, ensuring it seeps down into the crevices between the potato slices.
Scatter the remaining grated Gruyere cheese evenly across the top layer and dot the surface with small pieces of the remaining unsalted butter.
Bake uncovered in the preheated 190°C (375°F) oven for 55 to 60 minutes. The gratin is done when the potatoes offer no resistance to a paring knife and the top is deeply browned and bubbling.
Remove from the oven and allow the gratin to rest at room temperature for 15 minutes before serving. This allows the custard to set and ensures clean slices.
Chef's Notes
- Using a mandoline is crucial for this dish. Even 3mm slices ensure that the potatoes cook at the exact same rate, preventing an unpleasant mix of mushy and crunchy bites.
- Do not rinse your potatoes after slicing. The surface starches are absolutely essential to lightly thicken the milk and egg custard as it bakes.
- Waxy or all-purpose potatoes like Yukon Gold or Charlotte hold their structural integrity perfectly under the heat, while mealy baking potatoes like Russets may break down into a mush.
- Resting the gratin before slicing is non-negotiable. Slicing straight out of the oven will result in a soupy plate, as the starches and eggs need ambient cooling time to set fully into a sliceable consistency.
Storage
Refrigerator: 4 days — Store in an airtight container. The custard will firm up significantly.
Freezer: 1 month — Freezing may slightly alter the texture of the potatoes, but the dish remains highly enjoyable.
Reheating: Reheat portions in a 175 Celsius oven for 15 minutes, or microwave until hot.
