Ingredients:

  • 3 lbs (1.4 kg) Sweet Potatoes (approximately 3 large), peeled and sliced paper-thin (1.5mm)
  • 1 Tbsp (15g) Unsalted Butter, softened (for greasing the dish)
  • 1 tsp (5g) Kosher Salt (divided)
  • 2 cups (475 ml) Heavy Cream
  • 1 cup (240 ml) Whole Milk
  • ½ cup (100g) Light Brown Sugar, packed (divided)
  • 1 Tbsp (15 ml) Vanilla Extract
  • 1 tsp (5g) Ground Cinnamon
  • ½ tsp (2.5g) Freshly Grated Nutmeg
  • ¼ tsp (1.25g) Ground Ginger
  • 1 large pinch of Salt (for custard)
  • 1 cup (120g) Fresh or Frozen Cranberries
  • ½ cup (50g) Pecans, roughly chopped
  • 3 Tbsp (45g) Unsalted Butter, melted
  • 2 Tbsp (15g) All-Purpose Flour

Instructions:

  1. Preheat oven to 375°F (190°C). Generously grease the 9x13 inch baking dish with softened butter. Peel the sweet potatoes and slice them into uniform, very thin rounds (ideally 1.5 mm thick), using a mandoline or a sharp knife.
  2. In a large bowl, whisk together the heavy cream, whole milk, ½ cup brown sugar, vanilla extract, cinnamon, nutmeg, ground ginger, and salt until the sugar is mostly dissolved and the spices are well distributed.
  3. Arrange one-third of the sliced sweet potatoes slightly overlapping in the prepared baking dish. Season lightly with kosher salt.
  4. Scatter half of the cranberries evenly over the potato layer. Pour one-third of the cream mixture over the potatoes, ensuring the liquid flows between the slices.
  5. Repeat the process: Add the next third of the potatoes, the remaining half of the cranberries, and another third of the cream mixture.
  6. Top with the remaining sweet potatoes. Pour the rest of the cream mixture over the top. Press down gently with a spatula to ensure all potatoes are submerged.
  7. Cover the dish tightly with aluminium foil and bake for 35 minutes. This steaming process ensures the potatoes soften completely.
  8. While the gratin bakes, prepare the topping: combine the chopped pecans, melted butter, remaining 3 tablespoons brown sugar, and flour in a small bowl until the mixture resembles coarse sand.
  9. After 35 minutes, carefully remove the foil. Scatter the pecan crumble evenly over the gratin surface. Return the dish to the oven, uncovered, and bake for another 20–25 minutes. The topping should be golden brown and the potatoes completely tender when tested with a fork.
  10. Remove from the oven and let the gratin rest on a cooling rack for at least 15 minutes before serving. This allows the creamy custard to set and firm up.