There’s something magical about a bubbling casserole that comes out of the oven golden, cheesy, and inviting. For many of us, the scent of roasted veggies, smoky sausage, and melted cheese signals more than just dinner—it signals comfort, home, and family. This Keto Broccoli and Cauliflower Au Gratin with Sausage is one of those dishes that delivers on all fronts: hearty enough to satisfy, low in carbs for keto lifestyles, and quick enough to make even on a busy weeknight.

The beauty of au gratin dishes lies in their simplicity: humble vegetables elevated by a velvety cheese sauce, baked until bubbling perfection. Growing up, my grandmother’s potato au gratin was a staple at Sunday dinners, but now that we’re all more health-conscious, I love recreating that nostalgic flavor in a low-carb way. Enter broccoli, cauliflower, and sausage—a trio that transforms into a warm, cheesy, smoky bake you’ll want to make again and again.

Whether you’re preparing a family meal, planning your weekly keto menu, or simply craving something cheesy and satisfying, this dish will hit the spot. It’s cozy, nutrient-rich, and absolutely packed with flavor.

Ingredients:

3 cups broccoli florets
3 cups cauliflower florets
12 oz smoked sausage, sliced into coins
2 tablespoons butter
2 cloves garlic, minced
1 cup heavy cream
1 teaspoon Dijon mustard
1/2 teaspoon smoked paprika
1/2 teaspoon onion powder
1/4 teaspoon red pepper flakes (optional)
2 cups shredded cheddar cheese (divided)
1/2 cup grated Parmesan cheese
Salt and black pepper, to taste
2 green onions, sliced (for garnish)

Instructions:

Preheat oven to 375°F (190°C). Grease a medium casserole dish.
Steam or lightly boil the broccoli and cauliflower florets for 3–4 minutes until just tender but still crisp. Drain well and set aside.
In a large skillet over medium heat, melt the butter. Add garlic and sauté until fragrant (about 30 seconds).
Stir in the heavy cream, Dijon mustard, smoked paprika, onion powder, and red pepper flakes. Let the sauce simmer gently for 3–4 minutes until slightly thickened.
Add 1 1/2 cups of cheddar cheese and all of the Parmesan cheese to the sauce, stirring until smooth and creamy. Season with salt and pepper.
In the casserole dish, layer the broccoli, cauliflower, and sausage slices evenly. Pour the cheese sauce over the top, making sure everything is coated.
Sprinkle the remaining 1/2 cup of cheddar cheese on top.
Bake uncovered for 20–25 minutes until bubbly and golden brown.
Garnish with fresh green onions before serving.

Tips & Tricks:

For extra smoky flavor, use andouille sausage instead of regular smoked sausage.
Don’t overcook the vegetables before baking—they’ll continue cooking in the oven.
Add a pinch of nutmeg to the cheese sauce for a subtle flavor boost.

Keto Broccoli and Cauliflower Au Gratin with Sausage

A cheesy, low-carb casserole made with broccoli, cauliflower, and smoky sausage baked in a rich cheese sauce.

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Prep Time 15

Cook Time 25

Total Time 40

Servings: 6 servings

Course: Dinner, Main Course

Cuisine: American, Keto

Calories: 340

Ingredients Equipment Method Notes

Ingredients

3 cups broccoli florets
3 cups cauliflower florets
12 oz smoked sausage, sliced
2 tablespoons butter
2 cloves garlic, minced
1 cup heavy cream
1 teaspoon Dijon mustard
1/2 teaspoon smoked paprika
1/2 teaspoon onion powder
1/4 teaspoon red pepper flakes (optional)
2 cups shredded cheddar cheese (divided)
1/2 cup grated Parmesan cheese
2 green onions, sliced for garnish
Salt and black pepper, to taste

Equipment

Mixing bowls
Skillet
Casserole dish
Oven

Method

Preheat oven to 375°F (190°C). Grease a medium casserole dish.
Steam or lightly boil the broccoli and cauliflower florets for 3–4 minutes until just tender but still crisp. Drain well.
In a skillet, melt butter and sauté garlic until fragrant.
Stir in heavy cream, Dijon mustard, smoked paprika, onion powder, and red pepper flakes. Simmer until slightly thickened.
Add 1 1/2 cups cheddar and Parmesan cheese, stirring until smooth. Season with salt and pepper.
Layer broccoli, cauliflower, and sausage in casserole dish. Pour cheese sauce over top.
Sprinkle remaining cheddar cheese on top.
Bake uncovered 20–25 minutes until bubbly and golden brown.
Garnish with green onions before serving.

Notes

For best results, don’t overcook vegetables before baking.

Variations:

Swap the sausage for diced ham, rotisserie chicken, or turkey kielbasa.
Try a mix of cheeses like Gruyère, mozzarella, or Monterey Jack.
For a vegetarian version, skip the sausage and double up on veggies like zucchini or mushrooms.

Serving Suggestions:
This dish is filling enough to be the main course, but it also pairs beautifully with a crisp green salad, roasted asparagus, or even cauliflower rice.

Storage Information:
Store leftovers in an airtight container in the fridge for up to 4 days. To reheat, cover and warm in the oven at 325°F until heated through, or microwave individual portions. This dish can also be frozen for up to 2 months—just thaw overnight in the fridge before reheating.

FAQ:

Can I make this ahead of time? Yes! Assemble the casserole up to the baking step, cover, and refrigerate. When ready, bake as directed, adding 5 extra minutes.
Is this dish really keto-friendly? Absolutely. With heavy cream, cheese, and low-carb veggies, it’s both filling and keto-approved.
What sausages work best? Smoked, andouille, or even spicy chorizo all work well depending on your taste preference.

History / Fun Facts:
“Au gratin” is a French term meaning “by grating” or “with a crust.” Traditional gratins are made with potatoes and breadcrumbs, but in keto kitchens, we’ve learned to swap in cauliflower or broccoli for a satisfying low-carb twist. The technique of browning cheese or breadcrumbs on top dates back to French provincial cooking, but its popularity spread worldwide because who can resist a crispy, golden topping?

Keto Broccoli and Cauliflower Au Gratin with Sausage – A Cozy Low-Carb Comfort Bake