Cream of Mushroom With Roasted Garlic Cauliflower Au Gratin (No Roux)

50 min | easy | Mediterranean diet

Baked cauliflower au gratin in a white rectangular casserole dish, with cream sauce and melted mozzarella browned in spots over roasted florets, finished with a light sprinkle of chopped parsley.

Published Apr 22, 2026

Prep Time	Cook Time	Total Time
15 min	35 min	50 min

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Introduction

This creamy cauliflower au gratin skips the roux but still bakes up rich, cheesy, and full of roasted garlic flavor.

It is a cozy side dish for holiday dinners, Sunday suppers, or any weeknight meal that needs something extra comforting.

Baked cauliflower au gratin in a cream-colored casserole dish, with roasted florets coated in creamy cheese sauce and topped with browned, bubbly spots and a sprinkle of chopped parsley.

How to Make Cream of Mushroom With Roasted Garlic Cauliflower Au Gratin (No Roux)

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Preheat and prep the cauliflower

Heat the oven to 425°F and lightly grease a 2-quart baking dish.
Toss the cauliflower with olive oil until coated, then spread it on a sheet pan.
Roast the florets

Roast for 18 to 20 minutes, stirring once, until the edges turn golden and the centers just soften.
Do not overcook them here, because they will bake again in the sauce.

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Mix the creamy sauce

Whisk the soup, heavy cream, 3/4 cup mozzarella, Parmesan, garlic powder, salt, and pepper in a bowl.
Stir until the mixture looks smooth and the cheese is evenly distributed.
Assemble the gratin

Transfer the roasted cauliflower to the baking dish and pour the sauce over it.
Gently fold to coat, then scatter the reserved mozzarella across the top.
Bake until bubbly

Bake for 12 to 15 minutes, until hot, bubbling, and lightly browned on top.
Broil for 1 to 2 minutes if you want deeper color.

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Rest and serve

Let the gratin rest for 5 minutes before serving, so the sauce thickens slightly.
Serve as a side with roast chicken, steak, or baked ham.

Close-up of baked cauliflower au gratin in a yellow casserole dish, with tender florets coated in creamy melted cheese and browned, blistered tops, finished with a light sprinkle of chopped herbs.

Substitutions

Cream of mushroom soup for cream of celery soup: Cream of celery keeps the shortcut sauce silky and savory, with a lighter flavor that still fits the dish.
Mozzarella for fontina: Fontina melts smoothly and adds a nuttier taste, giving the gratin a richer, classic steakhouse feel.
Heavy cream for half-and-half plus sour cream: Use 1/3 cup half-and-half and 3 tablespoons sour cream for a lighter sauce with gentle tang.

Tips

Roast in one layer: Crowded cauliflower steams instead of browning, so use a large sheet pan and leave space around each piece.
Shred your own cheese: Freshly shredded cheese melts more smoothly because it lacks the anti-caking powders found in many packaged blends.
Check the seasoning before baking: Taste a coated floret before baking, since soup and Parmesan salt levels can vary quite a bit.
Rest before serving: A short rest helps the sauce set, so each spoonful stays creamy instead of running across the plate.

Nutrition Facts ^*

Energy	225	kcal
Protein	12	g
Total Fat	16	g
Carbohydrates	13	g
Dietary Fiber	4	g

^* Approximate, per serving.
Data source: USDA FoodData Central.

FAQ

Why did my gratin turn watery?: Cauliflower holds moisture, so roast it well and avoid covering the dish while it bakes. Letting it rest also helps the sauce tighten.
Can I make this ahead?: Yes. Roast the cauliflower and mix the sauce up to one day ahead. Assemble before baking, then add a few extra minutes in the oven.
How can I brown the top more?: Move the dish to the upper rack and broil briefly after baking. Watch closely, because cheese can darken fast.
Can I use frozen cauliflower?: Yes, but thaw and dry it very well first. Frozen florets release more water, so roasting is especially important.

Serving Suggestions

This creamy gratin pairs especially well with roast beef, pork tenderloin, or a holiday ham.

A pinch of red pepper flakes or extra Parmesan adds sharper contrast and better browning.

For a fuller mushroom note, stir in sauteed mushrooms before baking.

Recipe by Eunice.
“I learned to cook by standing in my grandma’s kitchen, watching her turn simple ingredients into meals that fed our entire family. That’s where it started. Today, I create recipes for real life, real kitchens, and anyone who wants good food without overthinking it.” Read more.