Brussels Sprouts Gratin

This Brussels sprouts gratin is really the next-level idea of how to prepare Brussels sprouts. No one will resist roasted Brussels sprouts smothered in creamy Gruyere cheese sauce, topped with crunchy breadcrumb parmesan topping and crispy bacon!

Ingredients

Below you will find information about the ingredients and how to prepare the recipe. For the measurements and detailed instructions scroll down to the printable recipe card.

Here´s what you need to make this delicious recipe:

• Brussels sprouts
• Bacon – it can also be omitted if you want this dish vegetarian.
• Cheesy and creamy Gruyere cheese sauce – you can swap Gruyere for Swiss cheese, fontina, cheddar, or Monterey Jack but Gruyere cheese is really the best. Its nutty and bold flavor is really amazing. You won´t need much for this recipe. Here you can find all my Gruyere cheese recipes. You can swap shallot for regular onion but then you will need to cook it a little bit longer until it is softened. Lemon juice is necessary in this recipe – it lightens up the otherwise heavy sauce – but don´t worry, the sauce won´t taste too lemony. While most recipes call just for heavy cream in this recipe, I swapped half of the cream for milk – the sauce is still delightfully creamy but not as heavy.
• Parmesan breadcrumb topping made with parmesan cheese, butter, and Panko breadcrumbs. I recommend using Panko breadcrumbs over regular fine breadcrumbs – they are far more crunchy.

How to make brussels sprouts gratin step by step

STEP 1 + 2: Bake bacon in the oven: Preheat the oven to 400°F (200°C).

Line a baking sheet with parchment paper, and lay bacon slices on the paper in a single layer (the slices can´t overlap but they can lay very close to each other). Bake for about 13 minutes (for very thin bacon slices) to 20 minutes (for thick bacon slices) or until browned and crispy (baking time will depend on the thickness of the slices and on the oven, keep an eye on it!).

Transfer to a plate (bacon will crisp up while cooling) and set aside.

Discard the parchment paper but reserve the bacon grease for baking Brussels sprouts. You will need about 3-4 tablespoons of bacon grease for the brussel sprouts. If you don´t have as much bacon grease left, use olive oil instead.

(3 1/2 ounces (100g) bacon)

STEP 3+4: Bake Brussels sprouts: Preheat the oven to 425°F (220°C), and move the wire rack one shelf above the center.

Prepare Brussels sprouts: wash them then pat dry with paper towels. Trim the bottoms, discard discolored outer leaves, and cut in half.

Bake your Brussels sprouts in two batches (or if you have a really large baking sheet you can try baking them at the same time but make sure the Brussels sprouts are not overcrowded or they won´t brown properly. Toss Brussels sprouts with bacon grease/olive oil and season with salt and pepper.

(2 1/2 pounds (1125g) brussels sprouts, 2 tablespoons olive oil)

Bake for 15 minutes or until browned and soft. Repeat with the second batch.

Reduce the oven temperature to 375°F (190°C).

STEP 5: Make the Panko parmesan topping: Melt the butter in a small pot, and stir in Panko until evenly coated in butter. Take the pot off the heat and stir in parmesan. Set aside.

(3 tablespoons (45g) butter, 3/4 cup (55g) Panko breadcrumbs, 1/2 cup (45g) grated parmesan cheese)

STEP 6: Add the Brussels sprouts to an oval 9×13-inch (23x33cm) baking dish or similar.

STEP 7: Make the sauce: Dice the shallot, finely chop garlic (with a knife and not a garlic press), juice the lemon, and grate the Gruyere on the large holes of a box grater.

(1 medium shallot, 4 cloves garlic, 1 tablespoon lemon juice, 1 cup (100g) Gruyere cheese, divided)

Melt the butter in a large pan, add the shallots, and cook over low heat for about 2 minutes or until softened. Add garlic, thyme, nutmeg, and flour. Cook for a minute, stirring.

(2 tablespoons butter, 1/2 teaspoon thyme, pinch of nutmeg, 1 1/2 tablespoons flour).

STEP 9: Add milk, cream, Dijon, and cook for 2-3 minutes, stirring, until thickened. Add 1/2 of the Gruyere cheese and cook until it´s melted.

(1 cup milk, 1 1/4 cups heavy cream, 1/2 teaspoon Dijon mustard)

Take the pan off the heat, season the sauce with lemon juice, salt, and pepper.

STEP 10: Assemble: add the sauce to the sprouts. Stir until combined. Top with the remaining 1/2 of Gruyere.

STEP 11: Sprinkle with breadcrumb parmesan topping.

Bake for 25-30 minutes (at 375°F / 190°C) or until the topping is golden and casserole hot and bubbly.

STEP 12: Take out of the oven and crumble baked bacon slices over the casserole.

Enjoy!

Storage

This dish is perfect to make ahead and reheat. It will be just a tiny bit less saucy/thicker but it tastes really good and the crunchy topping and bacon will still be crunchy.

I´m reheating it in the oven at 325°F (160°C) with a fan/convection setting (this is 350°F or 180°C if you don´t have a fan/convection setting) until warm.

You can keep it in the fridge for up to 4 days.

More Brussels sprout recipes you may enjoy

• Parmesan Roasted Brussels Sprouts
• Roasted Brussels Sprouts with Pineapple and Pecans
• Smashed Brussels Sprouts
• Shaved Brussels Sprout Salad
• Brussels Sprouts and Bacon

Did you make this recipe? RATE THE RECIPE or tell me in the COMMENTS how you liked it! You can also add a photo of your dish. It would make me very happy and will help other readers. Thank you!!