Butternut Squash Gratin with Leeks, Sage and Walnuts – a delicious vegetarian side dish, highlighting the best of fall ingredients, worthy of the holiday table! Vegan-adaptable!
- 2 lb butternut squash, peeled, sliced to 1/8 inch disks.
- 2 tablespoons olive oil or butter
- 2 medium leeks, thinly sliced
- 4 garlic cloves, rough chopped
- 15 sage leaves (8 more for crispy sage leaf garnish- optional)
- 1 cup heavy creamy (or sub half and half, or plant-based cream, or light coconut milk)
- 1/2 teaspoon salt and pepper
- 1/2 teaspoon nutmeg
- 1/2 teaspoon onion powder, optional
- 1/4 cup water or broth
- 3 ounces gruyere cheese (or sub parmesan or vegan parmesan)
- 1/2 cup toasted walnuts, chopped
Preheat oven to 375 F
- Prep Butternut: Peel and thinly slice the butternut squash into 18 -inch thick rounds. When you get to the seeds, scoop them out and continue slicing. Set aside 12-15 of the “prettiest” slices for the top of the gratin. ( There will be 3 layers of butternut – so you could divide into 3, placing any misshapen pieces in the middle layer)
- Cook the Leeks: Slice and rinse the leeks- the moisture here will help them soften. Heat oil or butter in a large skillet over medium heat. Saute the leeks, for 8-10 minutes, covering part way through so they soften. Add the garlic, sage and a pinch of salt, cook 2-3 more minutes. Turn heat off.
- Whisk the cream with the salt, pepper, nutmeg and onion powder in a medium bowl.
- Layer: Grease a large 9 x 13-inch baking dish or 11-12 inch round baking dish. A big shallow pan is BEST here ensuring even cooking. Grease the pan, add 1/4 cup water to the bottom of the pan. Layer with Butternut squash overlapping slightly. Sprinkle with half of the sauteed leeks. Drizzle with 1/3 cup cream mixture. Sprinkle with one ounce of Gruyere (about 3-4 tablespoons grated). Add the 2nd layer of butternut- using up any misshapen pieces here. Scatter with the remaining leeks. Drizzle with 1/3 cup cream mixture and sprinkle with grated gruyere cheese. Add the final layer of butternut, overlapping and pressing down so not domed in the middle. Drizzle the remaining cream mixture over top, lightly sprinkle with cheese and the walnuts. Give the pan a little shake, press down in the center again so gratin is level, not domed. Cover, using parchment first as a barrier, under the foil if the foil touches the top of gratin.
- Bake 45 minutes covered. Uncover, confirming the butternut is tender using the tip of a knife, then bake at 400 F uncovered, 15 minutes until beautifully golden.
- To make the crispy sage leave garnish, heat 1-2 tablespoons oil or butter in a pan over medium heat, add 8 whole sage leaves, sauteing each side 30 seconds or so until crisp (try a tester first) and place on a paper towel to cool for a couple of minutes. Arrange over the gratin.
This can be made ahead: Assemble ahea, refrigerate, and bake the day of serving, or alternatively, assemble and bake ahead, reheating the day of serving (350F, covered). Make sure to let this come to room temp before baking or reheating for most even cooking.
I have not tried this with cubed butternut, but if I were to go that route, I would toss them in a big bowl, with the cream mixture and leeks and cheese. Bake in a large shallow baking dish and allow 20-30 more minutes additional baking time depending on the size of the cubes. Thinly sliced butternut makes this bake relatively quickly- cubes would take longer, so plan accordingly. (Or you could lightly steam or cook them first?)
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