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Sweet Potato & Cranberry Gratin

A rich, creamy, and elegant holiday side dish featuring thinly sliced sweet potatoes layered with tart dried cranberries and a savory Gruyère cream sauce, baked with a caramelized top crust.
Print Recipe
Prep Time 20 minutes
Cook Time 1 hour 5 minutes
Total Time 1 hour 25 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 350
Ingredients Equipment Method Notes

Ingredients
  

The Base
  • 3 large sweet potatoes peeled and thinly sliced (approx. ⅛ inch)
  • 0.5 cup dried cranberries
The Cream Sauce
  • 1.5 cups heavy cream
  • 1 cup milk whole milk preferred
  • 2 cloves garlic minced
  • 1 tsp fresh thyme leaves or ½ tsp dried thyme
  • 0.5 tsp salt
  • 0.25 tsp black pepper
The Topping
  • 1 cup Gruyère or sharp white Cheddar cheese grated, divided
  • 2 tbsp brown sugar packed
  • 1 tbsp melted butter optional, for topping

Equipment

  • 9x13 inch casserole dish
  • Mandoline slicer (optional)
  • Medium saucepan

Method
 

  1. Preheat oven to 375°F (190°C). Grease a 9x13 inch casserole dish.
  2. Slice sweet potatoes thinly and uniformly (approx. ⅛ inch thick).
  3. In a saucepan, combine heavy cream, milk, garlic, thyme, salt, and pepper. Heat over medium until just simmering; remove from heat.
  4. Assemble the gratin in layers: one-third potatoes, one-third cream sauce, half the cranberries, and one-third of the cheese.
  5. Repeat the layering, then top with the final layer of potatoes and the remaining sauce (reserving the final one-third of the cheese for later).
  6. Cover tightly with aluminum foil and bake for 45 minutes, or until potatoes are tender.
  7. Remove foil. Sprinkle the remaining grated cheese over the top. Mix brown sugar with melted butter and sprinkle over the cheese.
  8. Bake uncovered for another 15-20 minutes until the top is golden, bubbly, and caramelized.
  9. Let rest for 10-15 minutes before serving.

Notes

You can assemble the gratin a day ahead and refrigerate. When baking from cold, add 10-15 minutes to the initial covered baking time.