This gratin is the ultimate way to show those healthy cruciferous brussels sprouts who's boss. Here's the thing, I don't eat heavy cheesy dishes every day, but special occasions can warrant good cheese, heavy cream, and butter. As a special occasion dish this is heaven. The brussels sprouts are roasted before they are assembled into a gratin making them buttery and caramelized, and the mornay sauce (simply a Béchamel sauce with grated cheese added to it) are so happy to be paired with these strong-tasting cabbage-y things.
Gratins are great make-ahead dishes. You can assemble them up to a day in advance and heat them up just prior to serving. They also tend to freeze well.
One note about brussels sprouts: the smaller the better. Sometimes you're limited to whatever the store or farmers' market has to offer. I lucked out and found young, fresh, tiny little brussels sprouts for this dish. I find that the smaller brussels are milder, more tender, and more delicious than the big ones. Certainly, this recipe will work with larger guys, I would just make sure to roast them for longer.
This dish would be great with a bright fresh light salad to balance out the richness of the gratin. It could be paired with your favorite savory entrée. For vegetarians, this side works super well alongside mushroom dishes.
Brussels Sprouts Gratin
Adapted from Saveur
3 lbs. brussels sprouts (about 3 pints), halved
4-6 tablespoons olive oil, or to taste
salt and pepper, to taste
3 tablespoons butter
3 tablespoons flour
2 cups whole milk
1 cup half & half or heavy cream
1/2 teaspoon freshly grated nutmeg
2 cups shredded Gruyere, Emmental, or Swiss
1/4 cup shredded Parmesan
Preheat the oven to 400°F.
Start by cleaning the brussels sprouts and removing any browned or tough outer leaves. Halve your brussels sprouts. In a large bowl, toss the brussels sprouts with the olive oil; make sure the sprouts are evenly coated in the oil. Season the sprouts with salt and pepper.
Transfer the seasoned brussels sprouts onto a baking sheet. Be careful not to crowd the sheet pan, you want to the sprouts to lie in a single flat layer so that they can evenly brown. Roast the sprouts until tender and browned, about 15-20 minutes depending on their size (check after 15 minutes and gage how much longer they need; they should be fully cooked).
Next, make the mornay sauce. Start by making a roux. Add 3 tablespoons butter to a medium saucepan (4-6 quart) on medium heat. Once the butter has just melted add the flour. Stir and cook until the mixture is golden brown and smells toasty, about 30-60 seconds. Slowly add the milk and half & half, continuously whisking the mixture as you add the liquid. Bring the liquid to a simmer, continuing to whisk so as to avoid lumps. Let the mixture thicken and simmer, about 2-3 minutes. Season with salt, pepper, and nutmeg. Remove from the heat and add the shredded cheese to the sauce. Stir until incorporated an you have a smooth sauce. Taste and adjust the seasoning if necessary.
Transfer the roasted brussels sprouts to an oval gratin dish (about 10-11 inches in length), or you can also use a 9 x 11 baking dish. Pour the mornay sauce over the roasted brussels sprouts. Top with parmesan and a few more gratings of nutmeg, or some additional black pepper.
Loosely cover with foil and bake for 15 minutes. Remove the foil and let the top of the dish brown, about 5 more minutes. Let the gratin rest for 10 minutes before serving.