Ingredients:

  • 3 lbs (1.4 kg) Sweet Potatoes, peeled and sliced uniformly thin (1/8 inch)
  • 1 cup (120 g) Dried Cranberries
  • 1 ½ cups (360 ml) Heavy Cream (35% Fat)
  • ½ cup (120 ml) Whole Milk
  • ¼ cup (50 g) Light Brown Sugar, packed (Custard)
  • 2 Large Eggs, lightly beaten
  • 1 tsp (5 ml) Vanilla Extract
  • 1 tsp (5 ml) Ground Cinnamon
  • ½ tsp (2.5 ml) Freshly Grated Nutmeg
  • ½ tsp (2.5 g) Kosher Salt (Custard)
  • ½ cup (60 g) All-Purpose Flour (Streusel)
  • ¼ cup (50 g) Light Brown Sugar, packed (Streusel)
  • ¼ cup (56 g) Cold Unsalted Butter, diced
  • ½ cup (60 g) Chopped Pecans
  • ¼ tsp (1 g) Salt (Streusel)

Instructions:

  1. Prepare and Pre-Bake Set-Up: Preheat oven to 375°F (190°C). Lightly butter the 9x13 inch gratin dish. Peel sweet potatoes and slice them uniformly thin—ideally 1/8 inch (3 mm) thick.
  2. Construct the Cream Custard: In a small saucepan, gently warm the heavy cream, whole milk, brown sugar, cinnamon, nutmeg, and salt over medium-low heat until the sugar dissolves. Remove from heat and stir in the vanilla extract.
  3. Temper the Eggs: In a separate bowl, lightly whisk the two eggs. Slowly drizzle about half a cup of the warm cream mixture into the beaten eggs while constantly whisking. Pour the tempered egg mixture back into the remaining warm cream mixture and whisk until fully combined and smooth.
  4. Layer and Assemble the Gratin: Arrange one-third of the sliced sweet potatoes in an overlapping shingle pattern across the bottom of the prepared dish. Scatter half of the dried cranberries evenly over the first layer. Pour one-third of the cream custard evenly over the potatoes and cranberries. Repeat this layering process once more. Top with the final layer of sweet potatoes and pour the remaining custard over the entire dish.
  5. Initial Bake (Covered): Cover the gratin tightly with foil. Bake for 30 minutes. (This covered phase ensures the potatoes cook fully and absorb the custard.)
  6. Prepare the Streusel Topping: While the gratin is baking, combine the flour, brown sugar, and salt in a bowl. Cut in the cold diced butter until the mixture resembles coarse crumbs. Stir in the chopped pecans.
  7. Final Bake and Rest: After 30 minutes, remove the foil. Sprinkle the prepared pecan streusel evenly over the top. Return the gratin to the oven, uncovered, for another 20–30 minutes, or until the topping is deeply golden brown and the potatoes are completely tender. Allow the gratin to rest for 10–15 minutes before serving.