Ingredients:

  • 2 Tbsp Unsalted Butter (30 g)
  • 3 large Garlic Cloves, finely minced
  • 3 lbs Potatoes (1.4 – 1.5 kg), such as Maris Piper or Russet, peeled and thinly sliced
  • 3 cups Double Cream (Heavy Cream) (700 ml)
  • 1 cup Whole Milk (240 ml)
  • 3 Tbsp Prepared White Horseradish (45 ml)
  • 1/2 tsp Freshly Grated Nutmeg (2.5 ml)
  • 2 tsp Sea Salt (10 g)
  • 1 tsp Freshly Ground Black Pepper (5 g)
  • 1/2 cup Gruyère or Aged Cheddar (60 g), finely grated (optional)

Instructions:

  1. Preheat the oven to 375°F (190°C). Generously butter a 9x13 inch deep baking dish.
  2. In a heavy-bottomed saucepan, melt the butter over medium heat. Add the minced garlic and sauté gently for 1 minute until fragrant (do not brown).
  3. Pour in the double cream and whole milk. Stir in the salt, pepper, horseradish, and nutmeg. Bring the mixture just to a simmer (do not boil rapidly) and immediately remove from the heat. Let the mixture steep for 5 minutes.
  4. Slice the peeled potatoes uniformly thin—ideally 1/8 inch (3 mm) thick, using a mandoline if possible. Do not rinse the sliced potatoes; the residual starch is needed to thicken the gratin.
  5. Arrange a layer of potato slices, slightly overlapping, covering the bottom of the prepared dish. Ladle a generous amount of the cream mixture over the first layer. Repeat this layering process until all the potatoes and cream are used, finishing with a layer of cream mixture on top. Press down gently to ensure the potatoes are submerged.
  6. Cover the dish tightly, first with parchment paper, then with aluminium foil. Bake for 45 minutes at 375°F (190°C) to steam-cook the potatoes.
  7. Remove the foil and parchment. Insert a sharp knife into the centre—it should meet minimal resistance, indicating the potatoes are nearly done.
  8. If using cheese, sprinkle the Gruyère or Cheddar evenly over the top. Return the dish to the oven, uncovered, and bake for an additional 25–30 minutes, or until the top is deeply golden brown and the cream is bubbling vigorously.
  9. Remove the gratin from the oven and let it rest on the counter for at least 15 minutes before serving. This resting period is essential to allow the gratin to set and prevent it from collapsing when cut.