There’s something undeniably comforting about a warm, cheesy casserole on a chilly evening. My love affair with mushrooms began years ago during a trip to the lush forests of Oregon.

I remember walking through the dew-laden woods, guided by an expert forager, learning about the countless varieties of fungi hiding in plain sight. The forest floor was alive with possibilities, and I couldn’t wait to bring some of that magic into my kitchen.

Fast forward to today, and mushrooms have become a staple in my cooking. They are versatile, hearty, and pack an umami punch that’s perfect for dishes like this deliciously cheesy mushroom casserole.

This recipe is a tribute to those misty mornings in Oregon—simple, comforting, and full of flavor. Plus, it’s keto-friendly and gluten-free, making it a wonderful option for almost everyone at the table.

The Ingredients You’ll Need

Mushrooms (300g): The heart of our casserole. Feel free to use any variety you like—white button, cremini, or a mix for added depth.
Onion (1 small): Adds a sweet, earthy base flavor that complements the mushrooms beautifully.
Garlic (1 clove): Just a hint of garlic enhances the overall flavor without overpowering the dish.
Thyme (1 tbsp, dried or fresh): This herb brings a touch of warmth and earthiness that pairs perfectly with mushrooms.
Cognac (30 ml, optional): A splash of cognac adds a sophisticated depth, but it’s entirely optional if you prefer to keep it alcohol-free.
Mozzarella (120g, shredded): Because what’s a casserole without some gooey, melted cheese?
Salt & Pepper: To taste.
Fresh Parsley: For garnish—adds a pop of color and a fresh, herbal note.

How to Craft the Perfect Mushroom Casserole

Preheat Your Oven: Start by preheating your oven to 400°F (205°C). A hot oven is key to achieving that perfect bubbly top layer of cheese.
Sauté the Mushrooms and Onions: In a large, deep skillet, heat some olive oil over medium-high heat. Add the mushrooms, onions, and a pinch of kosher salt. Sauté them together, stirring occasionally. Mushrooms have a high water content and will release a lot of liquid as they cook. You’ll want to continue cooking until most of this liquid has evaporated—this should take about 10 minutes.
Add the Flavors: Once the mushrooms have cooked down, add the garlic, black pepper, and thyme to the skillet. Stir and let them cook for about a minute, just until the garlic is fragrant.
Optional Touch of Cognac: If you’re feeling a bit fancy, now’s the time to add that splash of cognac. It’s an optional step, but it adds a rich, nuanced flavor that’s quite delightful.
Assemble the Casserole: Transfer the mushroom mixture to a prepared baking dish. Sprinkle the shredded mozzarella evenly over the top.
Bake to Perfection: Place the dish in the oven and bake for about 15 minutes, or until the casserole is hot and bubbly and the cheese has melted to a golden perfection.
Garnish and Serve: Remove from the oven, sprinkle with freshly chopped parsley, and serve hot.

Cooking Tips and Tricks

Choosing Your Mushrooms: Don’t be afraid to mix and match varieties. Cremini mushrooms offer a richer flavor, while shiitakes can add a meaty texture.
Why Sauté First? Sautéing the mushrooms and onions first is crucial. It helps release the excess moisture from the mushrooms, preventing your casserole from becoming too watery.
Cheese Choices: While mozzarella provides a classic, gooey texture, feel free to experiment with other cheeses like Gruyère or a sharp cheddar for a different flavor profile.

Common Variations

Vegan Option: Substitute the mozzarella with a vegan cheese alternative and use olive oil or vegan butter in place of regular butter. You can also skip the cognac or use a bit of vegetable broth instead.
Add Some Greens: Throw in some spinach or kale for added nutrition and color. Just be sure to sauté them along with the mushrooms to prevent excess water.

Chef’s Note

This cheesy mushroom casserole is a wonderful way to enjoy a cozy meal without spending hours in the kitchen. It’s perfect for a weeknight dinner but also elegant enough for a weekend gathering with friends. Pair it with a simple green salad and a glass of crisp white wine, and you’ve got a meal that’s as satisfying as it is easy to prepare.

Enjoy the comforting warmth and delicious flavors of this dish, and remember that sometimes, the simplest ingredients can create the most memorable meals. Bon appétit!

Cognac Mushroom Casserole

Mushrooms are one of my favorite vegetables (well, technically they’re fungi, not vegetables). You’ve probably already noticed this; I often share recipes where I use mushrooms ☺️ This deliciously cheesy mushroom casserole is wonderfully flavored with onions, thyme, and melted mozzarella. 👌Made without breadcrumbs and ready in about 40 minutes, it’s keto and gluten-free.

Print Recipe Pin Recipe

Prep Time 10

Cook Time 25

Total Time 35

Course Main Course

Cuisine Keto, Gluten-free

Servings 2

Ingredients

300 g Mushrooms
1 Onion small
1 Garlic cloves
1 tbsp Thyme Dried or fresh
30 ml Cognac Optional
120 g Mozzarella
Salt to your taste
Pepper to your taste
Fresh parsley for garnish

Instructions

Preheat your oven to 400 degrees F. (205 C)
Heat the olive oil in a large, deep skillet over medium-high heat. Add the mushrooms, onions, and kosher salt. Cook, stirring occasionally, until the mushrooms have released their liquid and the liquids have mostly evaporated, about 10 minutes.
Add the garlic, black pepper, and thyme. Cook, stirring, for one more minute. Remove from heat.
Add cognac if desired (Optional)
Transfer the mixture to the prepared baking dish. Sprinkle it with the shredded cheese.
Bake the casserole until hot and bubbly, about 15 minutes. Sprinkle with parsley and serve.