This Creamy Roasted Brussels Sprouts Gratin is the perfect holiday side dish! Tender-crisp vegetables are coated in a rich, decadent sauce and topped with a flavorful, crispy topping. This side dish is indulgent, delicious and guaranteed to hit the spot!Recipe can be scaled up or down by using the slider if you hover your mouse over the number of Servings.
Preheat Oven: Arrange oven rack to center position. Preheat oven to 400 degrees F. Spray a 2 quart gratin or baking dish with non-stick cooking spray. Set aside.
Prepare the topping: In a small mixing bowl, combine the panko, pine nuts, 1/2 cup gruyere, and 1/4 cup parmesan. Season with 1/8 teaspoon of salt and a pinch of pepper. Add in the melted and cooled butter. Stir well to combine. Set aside.
Par-bake Vegetables: Line a large, rimmed baking sheet with aluminum foil for easy clean up. Add brussels sprouts and onions. Drizzle with oil and season with 1/2 teaspoon salt and 1/4 teaspoon of pepper. Toss well to coat. Spread the vegetables out in an even layer. Bake for 15-20 minutes, tossing halfway through cooking, or until vegetables are almost fork tender. Remove from oven and transfer to prepared baking dish.
While the vegetables are baking, Make the Sauce (SEE NOTES): In a medium-size saucepan, melt the butter over medium heat. Add the flour and stir continuously for 1-2 minutes or until the mixture is blonde in color. While whisking constantly, gradually add in the cream. Add the nutmeg and season with 1/4 teaspoon of salt and 1/8 teaspoon of pepper. Bring mixture to a gentle simmer and reduce heat as needed to maintain a gentle simmer. Cook, whisking frequently, until the sauce is thickened and coats the back of a spoon, about 5-8 minutes. Turn off the heat. Add in 3/4 cup of gruyere cheese. Whisk until smooth. Add in 1/4 cup parmesan. Whisk until the cheeses are fully incorporated. Taste and adjust for seasoning with salt and pepper.
Assemble the gratin: Pour the sauce evenly over the brussels sprouts and onions in the prepared baking dish. Use a spatula to spread the sauce out in an even layer. Sprinkle the crunchy topping evenly over the sauce.
Bake: Bake gratin UNCOVERED, for 20-25 minutes or until the sauce is bubbling and the top is golden brown. If the top starts to brown too quickly towards the end of baking, lightly tent the dish with aluminum foil.
Rest and Serve: Allow to rest for 5 minutes before serving. Garnish with more parmesan and fresh thyme! Enjoy!
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Notes
Brussels Sprouts: You want the brussels sprouts to be uniform in size. If the brussels sprouts are huge, quarter them. If they are on the medium or small side, half them. You want them to be roughly the same size as the onions.
Onions: Frozen pearl onions are so much more convenient than fresh! Thaw the completely in the refrigerator overnight. Pat them thoroughly dry before proceeding with the recipe.
Cream: To ensure your sauce is lump-free, make sure you use room temperature (or close to it) heavy cream. Remove the cream from your refrigerator and let it sit on the counter while you prep all the ingredients.
The Creamy Sauce: Make sure you slowly whisk the cream into the roux (butter and flour mixture). Do this by adding the cream a little bit at a time, whisking until smooth between each addition. This will ensure your sauce is silky and thick!
Want to add Bacon? You can easily add bacon if desired! Scatter cooked, crumbled bacon on top of the par-roasted brussels sprouts and onions in the baking dish. Then, pour on the cheese sauce and top with crispy topping.
Nutritional information is an approximation based upon 6 servings. Exact information will depend upon the brands of ingredients and precise measurements used.