Deeply browned cremini mushrooms are enveloped in a silky shallot, garlic, thyme, and cream sauce, then finished with Gruyère, Parmigiano-Reggiano, and a crisp buttery panko topping. Rich, savory, and beautifully browned, this gratin makes an elegant steakhouse-style side dish for beef, pork, or roasted chicken.

Prep Time: 15 minutes
Cook Time: 35 minutes
Total Time: 50 minutes
Servings: 6
Difficulty: Level 2 — Easy
Cost: Level 3 — Moderate

Ingredients

Mushroom Base

• 1 1/2 pounds cremini mushrooms, cleaned and sliced 1/4 inch thick
• 2 tablespoons unsalted butter
• 1 tablespoon extra-virgin olive oil
• 1 large shallot, finely chopped
• 3 cloves garlic, finely minced
• 1 teaspoon fresh thyme leaves
• 1/2 teaspoon kosher salt, plus more to taste
• 1/4 teaspoon freshly ground black pepper
• 2 tablespoons dry sherry
• 3/4 cup heavy cream
• 1 teaspoon Worcestershire sauce
• 1/8 teaspoon freshly grated nutmeg

Gratin Topping

• 3/4 cup freshly grated Gruyère cheese, divided
• 1/3 cup finely grated Parmigiano-Reggiano cheese, divided
• 1/3 cup panko breadcrumbs
• 1 tablespoon unsalted butter, melted
• 1 tablespoon finely chopped fresh parsley

Instructions

Brown the Mushrooms

1. Preheat the oven to 400°F. Lightly butter a shallow 1 1/2- to 2-quart gratin or baking dish.
2. Heat the butter and olive oil in a large skillet over medium-high heat.
3. Add the mushrooms in as broad a single layer as possible. Cook in two batches if necessary rather than overcrowding the skillet.
4. Leave the mushrooms undisturbed for about 2 minutes, then continue cooking for 6–8 minutes, stirring occasionally, until their released moisture has evaporated and the mushrooms are deeply golden brown.
5. Add the shallot and cook for about 2 minutes, until softened.
6. Add the garlic and thyme and cook for 30 seconds, just until fragrant.

Make the Cream Sauce

7. Season the mushrooms with the salt and black pepper.
8. Add the sherry and scrape up the browned bits from the bottom of the skillet. Cook for 1–2 minutes, until the liquid has almost completely evaporated.
9. Add the heavy cream, Worcestershire sauce, and nutmeg. Reduce the heat to medium-low and simmer for 3–5 minutes, stirring occasionally, until the cream has thickened slightly and coats the mushrooms.
10. Stir in 1/2 cup of the Gruyère and 2 tablespoons of the Parmigiano-Reggiano. Cook just until the cheese has melted. Taste and adjust the seasoning as needed.

Assemble and Bake

11. Transfer the mushroom mixture to the prepared baking dish and spread it evenly.
12. Combine the remaining Gruyère, remaining Parmigiano-Reggiano, panko, and melted butter in a small bowl.
13. Sprinkle the topping evenly over the mushrooms.
14. Bake for 12–15 minutes, until the gratin is bubbling around the edges and heated through.
15. Switch the oven to broil and broil for 1–2 minutes, watching continuously, until the topping is crisp and deeply golden brown.
16. Let the gratin rest for 5 minutes. Sprinkle lightly with parsley and serve hot.

Cook’s Notes

Properly browning the mushrooms is the key to this dish. Mushrooms release considerable moisture as they cook; overcrowding the skillet traps that moisture and causes them to steam rather than brown. Use two batches if needed.

Allow most of the mushroom liquid to evaporate and some golden color to develop before adding the shallot and garlic.

The finished cream sauce should cling to the mushrooms rather than form a pool in the baking dish. If it appears too loose, simmer it for another minute or two before adding the cheese.

Freshly grated Gruyère and Parmigiano-Reggiano provide smoother melting and better browning than pre-shredded cheese.

Dry sherry contributes a subtle nutty complexity that works especially well with mushrooms. A dry white wine may be substituted.

Broilers vary considerably. Watch the gratin continuously during the final browning step and remove it as soon as the topping is deeply golden.

Serving Suggestions

Serve alongside grilled ribeye, filet mignon, New York strip, prime rib, roast beef, pork chops, or roasted chicken.

For a balanced steakhouse-style dinner, pair the gratin with roasted asparagus, green beans, broccolini, or a crisp green salad with a bright vinaigrette.

Because the gratin is already rich and creamy, simply seasoned grilled or roasted meats make particularly good companions.

Warm crusty bread or dinner rolls are useful for capturing the remaining mushroom cream sauce.

Beverage Suggestions

Cabernet Sauvignon: Its structure and dark-fruit character work particularly well when the gratin accompanies grilled or roasted beef.

Pinot Noir: Earthy, lighter-bodied Pinot Noir complements the mushrooms without overwhelming them.

Chardonnay: A moderately oaked Chardonnay pairs naturally with the cream, Gruyère, and Parmigiano-Reggiano.

Unsweetened Iced Tea: Its clean, slightly tannic character provides a refreshing contrast to the richness of the gratin.

Lemonade: The bright acidity and light sweetness provide an effective nonalcoholic counterpoint to the creamy mushrooms. [Agave Lemonade] Agave Lemonade⁠

Sparkling Water with Lemon: A simple choice that cleanses the palate without competing with the mushroom flavor.

Storage and Reheating

Refrigerate leftovers in an airtight container for up to 3 days.

For the best texture, reheat the gratin in a 325°F oven until warmed through, then uncover or briefly broil to restore the crisp topping.

Individual portions may be reheated in the microwave, although the breadcrumb topping will soften.

The mushroom mixture may be prepared through Step 10 up to 1 day in advance. Refrigerate the mushroom mixture and topping separately. Assemble just before baking and allow approximately 5 additional minutes of baking time when starting from cold.

Freezing is not recommended because the cream sauce may separate and the mushrooms can become watery after thawing.

Variations

Three-Mushroom Gratin: Replace up to one-third of the cremini mushrooms with sliced shiitake and oyster mushrooms for additional texture and complexity.

Porcini Mushroom Gratin: Rehydrate 1/4 ounce dried porcini mushrooms, drain well, finely chop, and add them with the browned cremini mushrooms for a deeper mushroom flavor.

Truffle Mushroom Gratin: Stir 1/4 teaspoon truffle oil into the finished cream sauce before transferring the mushrooms to the baking dish. Use sparingly so the truffle does not overwhelm the mushrooms.

No-Breadcrumb Gratin: Omit the panko and finish the gratin with the remaining Gruyère and Parmigiano-Reggiano for a softer, cheese-forward crust.

Individual Mushroom Gratins: Divide the mushroom mixture among six small oven-safe gratin dishes or ramekins and top individually. Begin checking them several minutes earlier because smaller portions will heat more quickly.