Baked cheesy mushroom casserole is an easy side dish: sliced button mushrooms tossed with olive oil, garlic powder and thyme, layered with cheddar and Parmesan, covered with heavy cream and finished with buttery breadcrumbs. In the oven the cream and mushroom juices turn into a rich, cheesy sauce under a golden crust. It takes 40 minutes and serves 6.
How to make it: Toss the mushrooms with the oil and seasonings and spread them in a greased 9×13 dish. Scatter the cheddar and Parmesan over them, pour on the cream and top with breadcrumbs mixed with melted butter. Bake at 375°F for 25 to 30 minutes, until golden and bubbling, then broil a few minutes for extra crunch if you like.
Why You’ll Love It
- 10 minutes of prep: toss, layer, pour and bake.
- No precooking: the mushrooms go into the dish raw and cook in the cream.
- Two cheeses: melty cheddar and nutty Parmesan.
- Vegetarian side: rich enough for a holiday table, easy enough for a weeknight.
Ingredient Notes
Mushrooms: 1 pound of button mushrooms, sliced evenly so they cook at the same rate. Cremini (baby bella) mushrooms work too and taste a little earthier.
Seasoning: 1 tablespoon olive oil, 1 teaspoon each of garlic powder and dried thyme, 1/2 teaspoon salt and 1/4 teaspoon black pepper.
Cheese: 1 cup shredded cheddar and 1/2 cup grated Parmesan.
Heavy cream: 1 cup. It mixes with the mushroom juices to make the sauce.
Breadcrumb topping: 1/2 cup breadcrumbs stirred with 2 tablespoons melted unsalted butter. It’s optional, but it adds the crunch.
Parsley: 2 tablespoons chopped, to garnish.
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Ingredients
- 1 lb button mushrooms, sliced
- 1 tbsp olive oil
- 1 tsp garlic powder
- 1 tsp dried thyme
- 1/2 tsp salt
- 1/4 tsp black pepper
- 1 cup shredded cheddar cheese
- 1/2 cup grated Parmesan cheese
- 1 cup heavy cream
- 2 tbsp unsalted butter, melted
- 1/2 cup breadcrumbs (optional)
- 2 tbsp fresh parsley, chopped
How to Make Baked Cheesy Mushroom Casserole
1. Heat the oven. Preheat your oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish to prevent sticking.
2. Season the mushrooms. In a mixing bowl, combine sliced mushrooms with olive oil, garlic powder, thyme, salt, and pepper. Toss to coat the mushrooms evenly.
3. Spread. Spread the seasoned mushroom mixture evenly across the bottom of the prepared baking dish.
4. Add the cheese. Sprinkle shredded cheddar and grated Parmesan cheese evenly over the mushrooms, creating a cheesy layer.
5. Add the cream. Pour the heavy cream evenly over the mushrooms and cheese, which will form a creamy sauce as it bakes.
6. Top. In a separate bowl, combine melted butter with breadcrumbs, stirring until well mixed. Sprinkle this breadcrumb mixture over the top of the casserole.
7. Bake. Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the sauce is bubbling around the edges.
8. Broil (optional). For an extra crispy topping, broil the casserole for an additional 2-3 minutes after baking. Watch closely to avoid burning.
9. Rest and garnish. Let the casserole rest for a few minutes. Garnish with freshly chopped parsley before serving.
Tips for the Best Mushroom Bake
- Clean mushrooms gently. Wipe them with a damp towel or rinse quickly and dry them well. Waterlogged mushrooms make a thin sauce.
- Slice evenly. Even slices cook through at the same time.
- Spread in one layer. A thin, even layer lets the juices reduce with the cream instead of pooling.
- Use heavy cream. Lighter milk can curdle and won’t thicken.
- Let it rest. A few minutes out of the oven lets the sauce settle and thicken.
- Watch the broiler. Breadcrumbs go from golden to burnt in seconds.
Which Mushrooms Work Best?
White button mushrooms are mild and inexpensive, and they’re what this recipe uses. Cremini, also called baby bella, are the same mushroom picked older, with a deeper, earthier flavor. A mix of button and cremini gives the best of both. For something special, add a handful of sliced shiitake or oyster mushrooms. Whatever you use, keep the total at about a pound so the cream and cheese still coat everything.
Variations
- Spinach: fold chopped spinach into the mushrooms before baking.
- Onion: add thinly sliced onion or shallots with the mushrooms.
- Gruyère or Swiss: swap them for the cheddar.
- Crunchy crackers: use crushed buttery crackers in place of breadcrumbs.
- Fresh herbs: use fresh thyme or rosemary instead of dried.
Storage & Reheating
Refrigerate leftovers within 2 hours and eat them within 3 to 4 days. Reheat covered in the oven until hot, to 165°F, then uncover for a few minutes to crisp the top.
What to Serve With It
Serve it next to steak, roast chicken, pork chops or a holiday roast, or spoon it over toast or rice for a meatless meal.
More cheesy sides: cheesy asparagus casserole, copycat Ruth’s Chris potatoes au gratin and roasted balsamic Brussels sprouts with feta. More mushroom recipes: creamy spinach and mushroom gnocchi, cheesy garlic butter mushroom stuffed chicken and smothered chicken with creamed spinach, bacon and mushrooms.
Frequently Asked Questions
Do I need to cook the mushrooms first?
No. They go in raw and cook in the cream as the casserole bakes.
Can I make it ahead?
Assemble it up to a few hours ahead without the breadcrumbs, refrigerate, then add the topping and bake.
Why is my casserole watery?
The mushrooms were wet, or it needed a few more minutes to reduce. Dry them well and let it rest before serving.
Can I use half-and-half?
Heavy cream works best; lighter dairy can separate.
Is this casserole vegetarian?
Yes, as long as your Parmesan is made without animal rennet.
Can I skip the breadcrumbs?
Yes. The casserole will be creamier with a cheesy top instead of a crunchy one.
How long do leftovers keep?
3 to 4 days in the refrigerator.
Final Notes
Dry the mushrooms, spread them in one layer and bake until golden and bubbling. If you add spinach or Gruyère, tell me in the comments how it turned out.
Baked Cheesy Mushrooms Casserole
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Ingredients
- 1 lb button mushrooms sliced
- 1 tbsp olive oil for seasoning
- 1 tsp garlic powder for seasoning
- 1 tsp dried thyme for seasoning
- 1/2 tsp salt to taste
- 1/4 tsp black pepper to taste
- 1 cup shredded cheddar cheese for topping
- 1/2 cup grated Parmesan cheese for topping
- 1 cup heavy cream for creamy sauce
- 2 tbsp unsalted butter melted, for breadcrumb topping
- 1/2 cup breadcrumbs optional, for crispy topping
- 2 tbsp fresh parsley chopped, for garnish
Instructions
- Preheat your oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish to prevent sticking.
- In a mixing bowl, combine sliced mushrooms with olive oil, garlic powder, thyme, salt, and pepper. Toss to coat the mushrooms evenly.
- Spread the seasoned mushroom mixture evenly across the bottom of the prepared baking dish.
- Sprinkle shredded cheddar and grated Parmesan cheese evenly over the mushrooms, creating a cheesy layer.
- Pour the heavy cream evenly over the mushrooms and cheese, which will form a creamy sauce as it bakes.
- In a separate bowl, combine melted butter with breadcrumbs, stirring until well mixed. Sprinkle this breadcrumb mixture over the top of the casserole.
- Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the sauce is bubbling around the edges.
- For an extra crispy topping, broil the casserole for an additional 2-3 minutes after baking. Watch closely to avoid burning.
- Let the casserole rest for a few minutes. Garnish with freshly chopped parsley before serving.
Notes
Nutrition
Nutrition values are estimates based on the listed ingredients and serving count. Actual values vary with brands, cuts and portion sizes.
