Can I assemble the whole gratin two days ahead instead of one?

One day is the safe, tested window. At two days the salted slices start to darken at the edges and the cream takes on the raw leek flavor. If you need two days, slice and salt the squash, cook the leeks, and store those components separately; assemble the pan the night before baking.

My gratin is bubbling at the edges but the center slices are still firm. What now?

The slices in the center were thicker, or the pan went in straight from the refrigerator without the extra covered time. Re-cover with foil and give it 10 more minutes, then test the very center with a knife again. Next time, check the first slices against a ruler until quarter inch becomes habit.

Can I use the precut butternut squash cubes from the store?

You can, but the dish changes character: cubes cook unevenly and cannot be shingled, so the gratin eats more like a bake. If cubes are what you have, cut any thick ones down, keep the salting step, and add 5 to 10 minutes to the covered bake. Slices from a whole squash are worth the ten minutes they take.

Why did my cream sauce look split when the gratin came out?

The cream probably boiled at some point, either while warming or under a too hot oven at the end. Warm it only to steaming, bake at 375°F as written, and let the pan rest the full 15 minutes; a sauce that looks loose at minute one usually pulls together as it rests.

What can I serve with this gratin besides turkey?

It is excellent beside a roast chicken or a beef tenderloin at other tables, and it can carry a vegetarian main course plate with a sharp green salad and cranberry sauce. The sweet squash and sage cream are flexible enough for any rich, savory centerpiece.

Butternut Squash Gratin With Sage Cream, Made Ahead

Ingredients

Scale

1 large butternut squash, about 3 pounds, peeled, seeded and cut into 1/4 inch half moons
1 1/2 teaspoons fine salt, divided
2 tablespoons butter, plus more for the dish
2 leeks, white and light green parts only, halved and thinly sliced, about 2 cups
2 garlic cloves, minced
10 fresh sage leaves, finely chopped, plus 6 whole leaves for the top
1 1/4 cups heavy cream
1/2 teaspoon black pepper
1/4 teaspoon freshly grated nutmeg
3/4 cup finely grated Parmesan, divided
1/2 cup panko breadcrumbs
1 tablespoon olive oil

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Instructions

Toss the squash slices with 1 teaspoon of the salt in a colander and leave for 20 minutes. Spread on clean towels and pat thoroughly dry.
Heat the oven to 375°F if baking today and butter a 2 quart baking dish.
Melt the butter in a skillet over medium heat and cook the leeks with a pinch of salt for 6 to 7 minutes, until soft and sweet. Stir in the garlic and chopped sage for 30 seconds.
Warm the cream in a small saucepan with the black pepper, the nutmeg, the remaining 1/2 teaspoon of salt and half of the Parmesan, only until steaming and melted. Do not boil.
Layer half of the squash slices in tight overlapping rows in the dish. Spoon over half of the leeks and pour over half of the warm cream. Repeat with the rest.
For make ahead: cover the dish tightly and refrigerate for up to 24 hours. Keep the panko, remaining Parmesan and olive oil in a dry container, outside the refrigerator.
On baking day, stir the panko, remaining Parmesan and olive oil together, scatter over the gratin and tuck in the whole sage leaves.
Bake covered with foil for 30 minutes (40 minutes from the refrigerator), then uncovered for 20 to 25 minutes, until bubbling around every edge and a knife slides into the center with no resistance.
Rest for 15 minutes before serving so the cream sets around the slices.

Author: Chef Rita
Prep Time: 25 minutes, plus 20 minutes salting
Cook Time: 55 minutes