Ingredients
For the Dish:
- 1 tablespoon unsalted butter, melted or cooking spray, for greasing
- 5 tablespoons extra-virgin olive oil
- 3 cups thinly sliced leeks (from 3 large leeks)
- 4 garlic cloves, minced
- 1 pound Brussels sprouts, trimmed and shredded
- 2 cups heavy cream
- 1 cup grated Gruyère cheese
- ½ cup freshly grated Parmesan cheese
- 1 teaspoon kosher salt
- ¼ teaspoon freshly cracked black pepper
- 2 teaspoons minced fresh thyme
- ¼ teaspoon ground nutmeg
For the Topping:
- 1 cup panko breadcrumbs
- Remaining ¼ cup Parmesan cheese (from total ½ cup)
- 3 tablespoons extra-virgin olive oil (from total 5 tablespoons)
Instructions
- Preheat and prepare the dish: Preheat your oven to 425°F (220°C) and position the oven rack in the center. Grease a 9×13-inch baking dish with melted unsalted butter or cooking spray to prevent sticking.
- Sauté leeks and garlic: In a large skillet, heat 2 tablespoons of olive oil over medium heat until shimmering. Add the sliced leeks and cook while stirring frequently until softened, about 4 minutes. Add the minced garlic and cook, stirring, until fragrant, about 1 more minute. Transfer this mixture to a large bowl.
- Combine Brussels sprouts and sautéed leeks: Add the shredded Brussels sprouts to the bowl with the sautéed leeks and garlic, and toss well to combine.
- Prepare creamy cheese sauce: Return the skillet to medium heat and add the heavy cream, Gruyère cheese, ¼ cup Parmesan cheese, kosher salt, black pepper, minced fresh thyme, and ground nutmeg. Stir constantly as you bring the mixture to a simmer, allowing the cheese to melt and the sauce to thicken, which takes about 3 minutes.
- Mix sauce with Brussels sprouts: Pour the thickened cheese sauce over the Brussels sprout mixture in the bowl. Toss thoroughly to coat all the vegetables evenly with the creamy sauce.
- Assemble and bake: Transfer the coated Brussels sprouts mixture into the greased baking dish and spread it out evenly. Place the dish in the preheated oven and bake until the Brussels sprouts become tender, approximately 20 minutes.
- Prepare breadcrumb topping: Meanwhile, in a small bowl, mix the panko breadcrumbs with the remaining ¼ cup Parmesan cheese and 3 tablespoons of olive oil until combined thoroughly.
- Add topping and finish baking: Remove the baking dish from the oven after the initial bake. Evenly sprinkle the panko breadcrumb mixture on top of the gratin. Return the dish to the oven and bake for another 5 to 6 minutes, or until the topping is golden brown and crispy.
- Serve: Once done, remove from oven and serve the Brussels Sprouts Gratin family-style, while warm and bubbly.
Notes
- For best results, shred the Brussels sprouts thinly so they cook evenly and absorb the creamy sauce well.
- You can substitute Gruyère with Emmental or Swiss cheese if unavailable, but Gruyère provides a distinctive nutty flavor.
- If you prefer a lighter dish, try substituting half-and-half for the heavy cream, but the gratin will be less rich and creamy.
- Leftovers can be refrigerated for up to 3 days and reheated in the oven to retain the crispy topping.
- Use fresh thyme for a brighter herbal note, but dried thyme can be used in a pinch (reduce quantity to 1 teaspoon).
- Prep Time: 15 minutes
- Cook Time: 32 minutes
- Category: Side Dish
- Method: Baking
- Cuisine: French
