Cheesy Keto Brussels Sprouts Casserole

This keto Brussels sprouts casserole combines the tender bite of roasted sprouts with the crunch of walnuts and a rich, flourless cheese sauce. It’s a flavorful low-carb, gluten-free side that works well for holiday meals, Sunday lunches, or any time you want a hearty vegetable dish.

We were pleasantly surprised by how much we enjoyed this gratin — even people who don’t usually choose Brussels sprouts went back for seconds. Leftovers heated up well for lunch the next day, making this an easy, make-ahead side.

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Are Brussels sprouts ketogenic?

Brussels sprouts are a good choice for a ketogenic diet: they are low in net carbs (about 5 g net carbs per 100 g), high in fiber, and rich in vitamins C and K. They add texture and nutrition to a low-carb meal without overpowering other flavors.

How to cook Brussels sprouts

If you grew up with boiled, soft sprouts, try changing the cooking method — roasting or baking brings out a nutty, caramelized flavor. For this recipe, the sprouts are trimmed and halved, arranged in a baking dish with walnuts, and baked under a creamy cheese sauce. The sauce is flourless, which keeps the dish naturally gluten free while still silky and satisfying.

If you’d like other ways to enjoy this vegetable, consider a blended Brussels sprout soup or a mixed gratin with cauliflower.

The ingredients

• Brussels sprouts — choose firm, green sprouts.
• Walnuts — chopped; other nuts like pecans or hazelnuts also work.
• Cream cheese — the base for a rich, low-carb sauce.
• Butter — unsalted recommended so you can control seasoning.
• Heavy cream — gives the sauce body and creaminess.
• Parmesan — freshly grated for best flavor.
• Mozzarella — grated; you can swap for a sharp cheddar if preferred.
• Garlic powder — or use fresh minced garlic if you like.
• Nutmeg — optional; a small pinch adds warmth to the cheese sauce.
• Salt & pepper — to taste.

How to make keto Brussels sprouts gratin

This gratin is simple: halved sprouts and chopped walnuts are placed in a baking dish, a creamy cheese sauce is poured over, extra cheese is scattered on top, and the whole dish is baked until bubbling and golden. The sauce is made without flour, keeping the casserole gluten free and low carb while still creating a smooth, indulgent coating.

Make the cheese sauce

Trim and halve the sprouts

Pour sauce over sprouts and walnuts

Bake until golden and serve

I love how straightforward this recipe is — any vegetable coated in a creamy cheese sauce is an instant crowd-pleaser. Serve it alongside a roast, grilled protein, or a hearty vegetarian main such as a nut roast.

Recipe tips

Add chopped bacon or diced ham before baking if you want a meatier flavor.

A strong cheddar can replace mozzarella for a sharper, tangier sauce; blue cheese will give an even more pronounced flavor.

Swap walnuts for pecans or hazelnuts if you prefer; they toast nicely and add texture.

Storage

You can prepare this dish ahead of time and refrigerate it unbaked, then bake when needed. Leftovers should be stored in an airtight container in the fridge for up to 3 days — reheat thoroughly before serving.

More low-carb side recipes

Brussels Sprout & Cauliflower Gratin

Pumpkin & Goat’s Cheese Gratin

Celeriac Gratin

Turnip Gratin Dauphinoise

This post was originally published in December 2018. The photos and content have been updated; the recipe remains the same.