Ingredients:

  • 2 large Butternut Squash (approx. 3.5 lbs), peeled, seeded, sliced ⅛-inch (3 mm) thick
  • 1 tbsp Unsalted Butter (for greasing the dish)
  • 1 ½ cups Heavy Cream (35% Fat)
  • 2 tbsp Fresh Sage, finely chopped, divided
  • ½ tsp Nutmeg, freshly grated
  • ½ tsp Garlic Powder
  • 1 tsp Kosher Salt
  • ½ tsp Black Pepper, freshly ground
  • 6 oz Gruyère Cheese, freshly grated
  • ½ cup Panko Breadcrumbs
  • 2 tbsp Unsalted Butter, melted (for panko)

Instructions:

  1. Preheat the oven to 375°F (190°C). Grease a 9x13 inch casserole dish generously with 1 tablespoon of butter.
  2. Peel, deseed, and slice the butternut squash as thinly and uniformly as possible (ideally ⅛ inch or 3 mm). Uniformity is crucial for even cooking.
  3. Create the Sauce: In a medium bowl, whisk together the heavy cream, salt, pepper, nutmeg, garlic powder, and half (1 tablespoon) of the fresh chopped sage.
  4. Assemble Layer 1: Lay the first third of the squash slices flat in the prepared dish, slightly overlapping. Pour one-third of the cream mixture evenly over the squash. Sprinkle one-third of the grated Gruyère over the cream.
  5. Repeat Assembly: Repeat the layering process two more times, using the remaining squash, cream mixture, and Gruyère cheese. Finish the top layer with the remaining cream and cheese.
  6. Create the Crumb Topping: In a small bowl, combine the panko breadcrumbs, the remaining 1 tablespoon of sage, and the 2 tablespoons of melted butter. Toss until fully coated.
  7. Cover & Chill: Sprinkle the panko topping evenly over the assembled gratin. Cover the dish tightly with foil. At this point, you can refrigerate the dish for up to 24 hours.
  8. Bake (Covered): Place the chilled gratin in the preheated oven. Bake covered for 30 minutes. (If baking immediately, start the covered bake for 20 minutes.)
  9. Check for Tenderness: Remove the foil. Pierce the centre of the squash with a fork or thin skewer. The squash should yield slightly.
  10. Bake (Uncovered): Return the gratin to the oven, uncovered, for an additional 15–20 minutes, or until the topping is deep golden brown, bubbly, and the squash is completely tender.
  11. Rest: Remove the gratin from the oven and let it rest on the counter for 10 minutes before serving. This allows the sauce to fully set up.