Unlike most French vegetable gratins which are made with Béchamel sauce (ie. see this Endive Gratin), this one is made with a heavy cream-based sauce. This sauce is simpler to make and more forgiving. The use of heavy cream also balances out the bitterness of the Brussels sprouts and makes for a rich and smooth sauce. 

Don’t skip on roasting the Brussels sprouts. 

Roasting the Brussels sprouts prior to dousing them in the sauce and baking the gratin serves two purposes. It first par-cooks them and ensure they will end up fork-tender in the finished baked gratin. But perhaps more importantly, roasting the brussel sprouts brings out their sweetness and creates a light caramelization all around. The sweet caramel notes of the roasted Brussels sprouts pairs perfectly with the creamy sauce and cheesy topping – and brings the flavors of this gratin to whole other level. 

Shopping for Brussels sprouts.

Members of the cabbage family, Brussels sprouts benefit from cool temperatures and are harvested in the Fall and Winter. You will often find Brussels sprouts in your grocery store year-round, but do know that the best, in-season ones are actually available from September through March in North America. These are sweeter and hence will develop a greater caramelization when being roasted! 

When shopping for Brussels Sprouts, looks for ones that are blemish-free, bright green,  with leaves tightly packed and that feel heavy for their size. They should feel firm when gently squeezed. The best Brussels Sprouts for this recipe are larger ones, which will be easier to slice in half. 

Notes about Gruyère

Gruyère cheese, hard Swiss-made cheese, is subtly salty with lovely nutty notes which pairs wonderfully with the rich creamy sauce. It also melts very well and turns crisp and golden on top, when put under the broiler. In France, Gruyère is affordable and widely available. It often comes pre-grated, sold in individual pouches. In the US/Canada,  Gruyère is a bit more costly than your average block of cheddar, but well worth it to use in this recipe. 

When seeking Gruyère at your grocery store, choose one that bears an AOP (Appellation d’Origine Protégée) seal. This sign on the label shows the cheese was made according to strict government mandated rules and quality standards. As alternatives for this recipe, Emmental, smoked white cheddar, Gouda, Fruilano or even extra-melty raclette cheese are also great options.

Can you prepare this Brussels Sprouts Gratin in advance? 

Yes, you can make this dish in advance – a few hours up to the day before. Prepare the dish up until it goes in the oven (until the end of step 4). Let the dish cool to room temperature, cover and refrigerate. Then, pre-heat your oven to 400°F (205°C), top off the gratin with the cheese and breadcrumbs and bake as directed. You will need to bake it a little longer (about 10 minutes additional) since the dish is going cold into the oven. 

I hope you’ll love this Roasted Brussels Sprouts Gruyère Gratin recipe as much as I do! If you have any questions, feel free to leave a comment. 

You may also like: 

• Classic French Quiche Lorraine
• Belgian Endive and Ham Gratin (Endives Au Jambon)
• French Green Beans Almondine
• Classic French Gratin Dauphinois
• Turnip & Carrot Gratin

Roasted Brussels Sprouts Gruyère Gratin

Print Recipe

Serves: 6-8 people Prep Time: 10 Minutes Cooking Time: 30 minutes 30 minutes

Nutrition facts: 200 calories 20 grams fat

Rating: 4.5/5

( 6 voted )

Ingredients

1 tbsp (14g) unsalted butter (to grease the dish)
1.3 lbs (600g) Brussels sprouts, ends trimmed and cut in half
¼ tsp salt
¼ tsp freshly ground black pepper
2 tbsp (30ml) Extra Virgin Olive Oil
1 tbsp (14g) unsalted butter
1 medium onion, peeled and diced
2 garlic cloves, peeled and finely diced
2-3 sprigs thyme, stemmed
2 tbsp (18g) all purpose flour
½ cup (130ml) heavy cream (35% m.f.)
1 cup (250ml) milk ( 2% or whole)
1/2 cup (50g) grated Gruyère cheese
1-2 tbsp bread crumbs

Instructions

Pre-heat your oven to 400°F (205°C) with a rack in the middle. Line up a baking sheet with parchment paper. 

Step 1 – Place halved Brussels sprouts in a large bowl, sprinkle with salt, black pepper and drizzle with extra virgin olive oil. Toss to coat and transfer Brussels sprouts onto prepared baking sheet. Scatter them into an even layer and transfer into the oven. Roast for 15 minutes, tossing the Brussels sprouts half way through, with a large spatula. 

Step 2 – While the Brussels sprout roast, melt butter in a large frying pan over medium heat. When the butter is melted, add the onion and cook for about 3-4 minutes until fragrant and translucent. Add garlic, thyme and cook for one more minute. Add the flour, stir and cook for about 2 minutes, until no dry flour remains (it should look moist and coat all the onion pieces). 

Step 3 - Add the heavy cream, stir and cook until it all comes together into a thick paste. Switch to a whisk and gradually add the milk and whisk until combined and smooth. 

Step 4 – Add the roasted brussels sprout to the sauce and stir to coat. Transfer brussels sprouts into the buttered baking dish and sprinkle with grated cheese and bread crumbs.

Bake for 15 minutes, and finish with 1 minute under the broiler.

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