📝 About This Recipe
This luxurious gratin marries the earthy, nutty sweetness of roasted chestnuts with the charred, savory depth of Brussels sprouts. Bathed in a velvety cream sauce infused with garlic and thyme, the dish is finished with a golden, bubbling crust of Gruyère and buttery sourdough crumbs. It is a sophisticated holiday classic that elevates the humble sprout into a centerpiece-worthy side dish.
🥗 Ingredients
The Vegetables
- 2 pounds Brussels sprouts (trimmed and halved lengthwise)
- 1.5 cups Cooked chestnuts (peeled, vacuum-packed or jarred, roughly halved)
- 2 tablespoons Olive oil
- 1 teaspoon Kosher salt (plus more to taste)
- 1/2 teaspoon Black pepper (freshly cracked)
The Cream Sauce
- 3 tablespoons Unsalted butter
- 2 pieces Shallots (finely minced)
- 3 cloves Garlic (minced)
- 1.5 cups Heavy cream
- 1 tablespoon Fresh thyme (leaves only, chopped)
- 1/4 teaspoon Nutmeg (freshly grated)
- 1 teaspoon Dijon mustard (for a subtle tang)
The Gratin Topping
- 1.5 cups Gruyère cheese (freshly grated)
- 1/2 cup Sourdough breadcrumbs (coarse, panko can be substituted)
- 1/4 cup Parmesan cheese (finely grated)
- 1 tablespoon Fresh parsley (finely chopped for garnish)
👨🍳 Instructions
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1
Preheat your oven to 400°F (200°C). Grease a 9x13 inch baking dish or a 2-quart gratin dish with a little butter.
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2
Toss the halved Brussels sprouts with olive oil, salt, and pepper on a large rimmed baking sheet. Spread them in a single layer.
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3
Roast the sprouts for 15-18 minutes until they are bright green and starting to brown on the edges. Remove from the oven and set aside.
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4
While the sprouts roast, melt 3 tablespoons of butter in a medium saucepan over medium heat.
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5
Add the minced shallots and cook for 3-4 minutes until translucent and soft. Stir in the garlic and cook for another 60 seconds until fragrant.
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6
Pour in the heavy cream, thyme, nutmeg, and Dijon mustard. Bring to a gentle simmer, then reduce heat to low and let it thicken slightly for 5 minutes. Season with a pinch of salt.
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7
In the prepared baking dish, combine the roasted Brussels sprouts and the halved chestnuts. Toss gently to distribute the chestnuts evenly.
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8
Pour the warm cream sauce over the sprout and chestnut mixture. Use a spoon to ensure the sauce seeps into the crevices.
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9
In a small bowl, mix the grated Gruyère, Parmesan, and breadcrumbs together.
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10
Sprinkle the cheese and crumb mixture evenly over the top of the gratin.
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11
Bake in the oven for 15-20 minutes, or until the sauce is bubbling vigorously and the topping is a deep golden brown.
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12
If you want a deeper crust, turn on the broiler for the last 1-2 minutes, watching closely to prevent burning.
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13
Remove from the oven and let rest for 5 minutes to allow the sauce to set. Garnish with fresh parsley before serving.
💡 Chef's Tips
Always grate your own Gruyère; pre-shredded cheese is coated in potato starch which prevents a smooth melt. If the sprouts are very large, quarter them instead of halving to ensure they soften at the same rate as the chestnuts. Don't skip the roasting step; boiling sprouts makes them mushy, while roasting adds a crucial nutty char. For a vegetarian-plus twist, add 1/4 cup of crispy pancetta or bacon bits into the mix before baking. Make-ahead tip: You can roast the sprouts and make the sauce a day early, then assemble and bake when ready.
🍽️ Serving Suggestions
Pairs beautifully with a crisp, dry white wine like a Chablis or an oaked Chardonnay. Serve alongside a roast turkey or a glazed ham for the ultimate holiday spread. Excellent as a vegetarian main course when served over a bed of creamy polenta. Accompany with a simple arugula salad dressed in lemon vinaigrette to cut through the richness of the cream.