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Ruth’s Chris Creamy Mushroom Au Gratin

Featured in Satisfying Main Courses.

This dish features tender mushrooms sautéed in butter with garlic and shallots, gently simmered in a creamy blend of Parmesan and Gruyère cheeses, thyme, and subtle seasoning. The mixture is baked until bubbling and golden, creating a rich, velvety sauce that complements the earthy mushrooms beautifully. Resting before serving lets the sauce thicken perfectly, providing a comforting, flavorful side or main that highlights simple, fresh ingredients.

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Barbara Chef
Updated on Wed, 10 Dec 2025 21:51:50 GMT
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A bowl of food with a fork in it. | gracefulflavors.com

This creamy mushroom au gratin is a luxurious side dish that pairs wonderfully with steaks, roasts, or even a simple weeknight dinner. The combination of earthy mushrooms and rich cheeses in a velvety cream sauce makes it an irresistible comfort food that feels fancy but is actually quite simple to prepare.

I first made this on a chilly weekend and now it’s become a favorite whenever I want something a little extra. The creamy sauce with those browned mushroom edges is pure indulgence.

Ingredients

  • Mushrooms cremini or white: provide an earthy, meaty base choose firm, fresh ones without blemishes
  • Butter: adds richness and helps sauté the mushrooms to golden perfection
  • Garlic: infuses the dish with savory aromatics use fresh minced cloves for the best flavor
  • Shallot: offers a mild onion flavor that blends smoothly into the cream sauce
  • Heavy cream: creates the silky texture that makes this dish feel indulgent
  • Parmesan cheese: adds sharp, nutty notes opt for freshly grated if possible
  • Gruyère or Swiss cheese: melts beautifully and adds a slightly sweet, nutty character
  • Thyme: introduces subtle herbaceous warmth
  • Black pepper: for gentle spice and depth
  • Salt: essential for balancing and enhancing all the flavors
  • Extra Parmesan and Gruyère: to build a golden, bubbling cheesy crust

Step-by-Step Instructions

Sauté the Mushrooms:
Melt the butter in a skillet over medium heat. Add the sliced mushrooms and cook until softened and lightly browned. This step concentrates the mushroom flavor and adds texture.
Add Aromatics:
Stir in the minced garlic and diced shallot. Cook for one to two minutes until fragrant, being careful not to brown the garlic too much to avoid bitterness.
Make the Cream Sauce:
Pour in the heavy cream and stir continuously. Add the grated Parmesan, shredded Gruyère, thyme, salt, and black pepper. Let the mixture simmer gently for three to four minutes until it thickens slightly. This thickened sauce will cling beautifully to the mushrooms.
Prepare for Baking:
Transfer the creamy mushroom mixture into a small baking dish and spread it out evenly. This helps the dish bake through uniformly.
Add Topping and Bake:
Sprinkle extra Parmesan and Gruyère generously over the top. Place the dish in a preheated oven at 400 degrees Fahrenheit and bake for 15 to 20 minutes until the top is golden brown and bubbly.
Rest Before Serving:
Allow the au gratin to rest for a few minutes before serving. This lets the sauce thicken up nicely for the perfect creamy texture.
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A bowl of Creamy Mushroom with a spoon in it. | gracefulflavors.com

I adore the Gruyère in this dish because it melts so smoothly and adds a nutty complexity that balances the mushrooms perfectly. One family memory that sticks with me is serving this alongside a holiday roast where everyone reached for seconds without a word—just pure satisfaction.

Storage Tips

Let leftovers cool to room temperature before sealing in an airtight container. Store in the refrigerator for up to three days. Reheat gently in the oven or microwave to keep the sauce creamy without breaking.

Ingredient Substitutions

Try cremini mushrooms for a more intense flavor or white button mushrooms for a milder taste. If you don’t have Gruyère, Swiss cheese is a good swap though it may be a bit less creamy. Heavy cream can be replaced with half and half mixed with a little butter for a lighter version though the sauce won’t be quite as rich.

Serving Suggestions

Serve this au gratin alongside a juicy steak, roast chicken, or pork tenderloin. It also makes a great vegetarian main course paired with a crisp salad or roasted root vegetables.

Cultural Context

Au gratin dishes originated in French cuisine, traditionally featuring vegetables or potatoes topped with cheese or breadcrumbs then baked until crisp and golden. This mushroom version adds a rustic twist to a classic technique by showcasing mushrooms as the star ingredient.

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A bowl of food with a spoon in it. | gracefulflavors.com

Frequently Asked Questions

→ What types of mushrooms work best for this dish?

Cremini or white mushrooms are ideal due to their firm texture and earthy flavor which hold up well during sautéing and baking.

→ Can I substitute the Gruyère cheese?

Swiss cheese is a great alternative that provides a similar melt and nutty taste complementing the Parmesan.

→ How do I ensure the sauce thickens properly?

Simmer the cream and cheese mixture gently after adding to the mushrooms, then let the dish rest after baking to allow the sauce to set.

→ What herbs enhance the flavor in this preparation?

Thyme is used here for its subtle, earthy aroma that balances the richness of the cream and cheese.

→ Is it necessary to rest the dish before serving?

Yes, letting the dish rest helps the sauce thicken and settle, improving texture and flavor intensity.

Creamy Mushroom Au Gratin

Sautéed mushrooms with creamy cheese sauce, topped with Parmesan and Gruyère, baked for a golden finish.

Prep Time
15 Minutes
Cook Time
25 Minutes
Total Time
40 Minutes
By: Barbara

Category: Hearty Mains

Difficulty: Easy

Cuisine: American

Yield: 5 Servings (4–6 servings)

Dietary: Low-Carb, Vegetarian, Gluten-Free

Ingredients

→ Mushrooms

01 1 lb cremini or white mushrooms, sliced

→ Dairy

02 2 tbsp unsalted butter
03 1 cup heavy cream
04 1/2 cup grated Parmesan cheese
05 1/2 cup shredded Gruyère or Swiss cheese
06 Extra grated Parmesan and Gruyère for topping

→ Aromatics & Seasonings

07 2 cloves garlic, minced
08 1 shallot, finely diced
09 1/2 tsp dried thyme
10 1/4 tsp freshly ground black pepper
11 Salt, to taste

Instructions

Step 01

Set the oven temperature to 400°F (200°C) and allow it to fully preheat.

Step 02

Melt butter in a skillet over medium heat. Add sliced mushrooms and cook until softened and lightly browned, about 5–7 minutes.

Step 03

Incorporate finely diced shallot and minced garlic into the skillet. Cook for 1–2 minutes until fragrant.

Step 04

Pour in heavy cream and add grated Parmesan, shredded Gruyère, dried thyme, salt, and black pepper. Stir to combine.

Step 05

Allow the mixture to simmer gently for 3–4 minutes, stirring occasionally, until the sauce thickens slightly.

Step 06

Move the creamy mushroom mixture into a small baking dish, spreading it evenly across the bottom.

Step 07

Sprinkle extra grated Parmesan and Gruyère evenly over the surface for a golden crust.

Step 08

Place the dish in the preheated oven and bake for 15–20 minutes or until the top is golden brown and bubbling around the edges.

Step 09

Remove from the oven and let rest for a few minutes to allow the sauce to thicken for optimal texture before serving.

Notes

  1. Resting the dish after baking helps the sauce set, preventing it from becoming too runny when plated.

Tools You'll Need

  • Skillet
  • Small baking dish
  • Oven

Allergy Information

Please check ingredients for potential allergens and consult a health professional if in doubt.
  • Contains dairy products

Nutrition Facts (Per Serving)

It is important to consider this information as approximate and not to use it as definitive health advice.
  • Calories: 350
  • Total Fat: 32 g
  • Total Carbohydrate: 8.5 g
  • Protein: 12 g