Ingredients:

  • 5 lbs (1.15 kg) Sweet Potatoes, peeled and thinly sliced
  • 6 oz (170 g) Gruyère Cheese, freshly grated
  • 1 Tbsp (15 g) Unsalted Butter
  • 1 large Shallot, finely minced
  • 2 cloves Garlic, crushed or minced
  • 1 Tbsp (5 g) Fresh Sage Leaves, finely chopped
  • 1 cup (240 ml) Double Cream (Heavy Cream)
  • 1/2 cup (120 ml) Whole Milk
  • 1 tsp Kosher Salt, plus extra for seasoning layers
  • 1/2 tsp Freshly Ground Black Pepper
  • 1/4 tsp Freshly Grated Nutmeg

Instructions:

  1. Preheat the oven to 375°F (190°C). Lightly butter a 9-inch (23 cm) round or oval shallow tian dish.
  2. Peel the sweet potatoes. Using a mandoline or a very sharp knife, slice them into even, thin rounds (2-3 mm / 1/8 inch). Grate the Gruyère cheese and set aside.
  3. Melt the butter in a small saucepan over medium heat. Add the minced shallot and cook until softened (3–4 minutes). Add the garlic and sage; cook for 1 minute until fragrant.
  4. Pour in the double cream and milk. Add the salt, pepper, and nutmeg. Bring the mixture just to a simmer (do not boil). Remove from heat and set aside briefly to infuse.
  5. Lay a tight, overlapping layer of sliced sweet potatoes on the bottom of the prepared dish, covering the entire base. Season this layer lightly with salt and pepper.
  6. Ladle about 2–3 tablespoons of the warm cream mixture over the potatoes. Sprinkle about 2 tablespoons of the grated Gruyère evenly over the cream.
  7. Continue the layering process—Potatoes, Seasoning, Cream, Cheese—until all the potatoes are used, pressing down slightly on each layer to ensure they settle.
  8. Pour the remaining cream mixture evenly over the top layer. Finish with the remainder of the Gruyère cheese.
  9. Cover the tian dish tightly with foil. Bake for 30 minutes at 375°F (190°C).
  10. Remove the foil. Increase the oven temperature slightly to 400°F (200°C) if needed, and bake for a further 20–25 minutes, or until the potatoes are tender when pierced and the top is deeply golden and bubbling.
  11. Remove the tian from the oven and allow it to rest for 10 minutes before serving. This crucial step allows the cream to re-set and the layers to hold their structure beautifully.