Vegetarian Stuffed Portobello Mushrooms are loaded with your favorite herb-infused stuffing, extra kale, and an indulgent dose of gruyere cheese. They’re hearty and full of texture, making them a perfect dinner option!
When it comes to vegetarian dinner recipes, mushrooms are one of those ingredients that deliver in terms of umami flavor, heartiness, and that “meaty” texture.
And then, go ahead and make large portobello mushroom caps the star of the show and you have yourself a real winner. These stuffed mushrooms are filled with a version of my favorite Thanksgiving herb stuffing, so essentially crusty bread, fresh herbs, and a delicious onion mixture.
Paired with melty cheese and the addition of kale, it’s a whole texture-filled, flavor-filled, your-tummy-will-be-filled kind of meal.
How to Clean and Prepare Portobella Mushrooms
I’m so glad you asked. Because this is v. v. important. There are a few steps to preparing the whole mushrooms for this recipe, so let’s start with the most important.
First: Wipe the Mushrooms Clean
When it comes to cleaning mushrooms, do not rinse your mushrooms under running water. Once in a while, a super quick rinse will do, but you do not want to soak them in water for an extended period of time.
Soaking mushrooms in water basically infuses them with dirty water. Mushrooms are super porous, like sponges, and if they’re soaked while dirty, that dirt water fills the pores and is just yucky.
Instead of rinsing or soaking the mushrooms, take a damp rag and wipe them clean.
You can use a damp paper towel or a reusable rag. I have a specific towel that I use (because yes, it WILL get dirty). It’s my “mushroom cleaning” towel.
Simply wipe the outside of the mushroom caps clean, rotating the towel every so often to have a clean area to wipe with.
Remove the Stems and Gills
After cleaning, remove the stems and scoop out the insides – the “gills”. The gills are those really narrow flaps on the bottom part of the mushroom. Removing the gills isn’t entirely necessary, because they are edible.
However, scooping them out provides more room for the filling. They also hold a lot of moisture, so we’re reducing the amount of water that cooks out, too.
Gently pull the stem off of the mushroom. Then use a spoon to carefully scrape out the gills, discarding them as you go.
How to Cook Portobellos
I’d much rather cook them than spell them, but for the record, I’m pretty sure you can spell them portabella, too. Google corrected me every time, so Os we’re going with it. Onto the goodness…
The key to cooking mushrooms is to first let the water seep out. No matter what kind of recipe you’re making, they’re going to release water. And you don’t want it to water down your recipe.
So before you stuff these mushrooms, first bake them for 10 minutes. This way, they’ll release some water and reduce the chances of a soggy filling. Add a dash of salt before baking, too, to help those liquids release (and hello, flavor).
After baking, you’ll notice that water has pooled inside the mushroom caps. Pour it into the sink to drain it out.
The bottoms need to stay nice and firm, too though. So here’s the key to preventing soggy mushroom bottoms. Are you ready for it?
Use an oven-safe cooling/wire rack placed inside your baking sheet.
Technically you can make these without the rack. However, the bottoms will get soggier than they would if you use a rack.
And we definitely don’t want soggy bottoms…so on the rack they go.
Make the Stuffing
We have a double meaning here because we are stuffing portobello mushrooms…and we’re using stuffing.
I first created this recipe for a local cooking class I hosted several Thanksgivings ago, and basically, I was looking for any and every way to have my favorite Vegetarian Herbed Stuffing more times than just the holidays.
And I did it. I figured it out and by the grace of all things good, it’s even better than I could’ve imagined.
We have traditional stuffing (ok, dressing if you want to be so super technical). It starts with dried-out bread cubes. Yes, let them dry out, this helps them hold their shape when the egg and vegetable stock are added.
Sauté onion, celery, garlic, and kale. The kale is a special addition to this version of the stuffing to make sure there was a little more oomph – and color. And in goes fresh sage, thyme, and garlic for even more flavor.
Also, be sure to stir in shredded gruyere cheese. It’s nutty and creamy and one of the best cheeses to use in the fall because it pairs so well with fall flavors (gruyere and thyme is my favorite combination!). It’s also really good with mushrooms. Checking all the boxes here friends!
Note: not all cheese is strictly vegetarian; be sure to check the labels to find a cheese that meets your needs. You’ll want to look for microbial enzymes or kosher cheese.
Then, stir in vegetable stock and the whisked egg until the mixture is damp, but not soaking. This keeps it moist, but we don’t want it to end up soggy (are you sensing the theme?).
Fill the Mushroom Caps
Now that the stuffing is prepared and the mushroom caps have completed their first bake to get the liquid outta there – it’s finally time to stuff the mushrooms!
Divide the kale and gruyere stuffing mixture between the mushroom caps, piling it on high, and pressing down as needed so it doesn’t fall out.
Then, for good measure, of course, add another sprinkle of cheese on top before baking.
Place foil tented over the top of the baking sheet for the first 15 minutes. Then, remove the foil for the remaining time (about 15 minutes) and bake until the cheese is melty and golden brown. The edges of the bread will get crispy too – so good!
Before serving, garnish with fresh herbs like additional thyme or parsley.
What to Serve with Portobello Mushrooms
These stuffed mushrooms make an excellent meatless main dish, and there are a variety of recipes you can serve with them, depending on which direction you’d like to go with it.
To keep the rest of the meal light, I’d recommend serving them with a green salad. Toss some greens with a maple balsamic vinaigrette or white balsamic vinaigrette. The acidity will balance out the savoriness of the stuffed mushrooms so nicely.
To keep the vibe warm, cozy, and comforting, serve with a vegetarian soup. The creamy texture of both the butternut squash soup and vegan broccoli soup would complement this recipe nicely. And you cannot go wrong with this creamy potato soup, either.
Make Ahead and Storage
There are a few routes you can take to make these stuffed mushrooms ahead of time.
- Assemble completely. This includes cooking the mushrooms for the first bake, and stuffing them. Then, store them in an airtight container up to 1 day in advance until you’re ready to finish baking them. Or;
- Prepare the stuffing on its own, but do not assemble or prebake the mushrooms. This can be done up to two days in advance.
For leftover stuffed mushrooms, place them in an airtight container in the fridge for up to 3-4 days. Reheat them in the oven (350°F-ish) or air fryer (325°F) until heated through. You can also reheat them in the microwave, although their texture won’t be quite as good.
You can easily adjust this recipe to make it your own. Here are a few ideas:
- Add parmesan cheese to the mixture – or simply use another cheese! Fontina and gouda both have strong, nutty, and creamy flavors similar to Gruyere. You could also go milder with swiss or mozzarella.
- Swap kale for spinach or another leafy green.
- Add additional veggies like zucchini, carrots, or even sun-dried tomatoes for extra umami!
- Drizzle a balsamic vinegar glaze after baking.
- Make it gluten-free by using gluten-free bread! Similarly, make it dairy-free by using vegan cheese.
Did you make this recipe? Please leave a star rating and review in the form below. I appreciate your feedback, and it helps others, too!
Vegetarian Herb Stuffed Portobello Mushrooms
- 4 large portobello mushroom caps, gills and stems removed
- 6 Tablespoons unsalted butter
- 1 cup yellow onion, finely diced
- ¾ cup celery, small dice
- 2 garlic cloves, minced
- ¾ teaspoon fine sea salt, more to taste
- ¾ teaspoon freshly ground black pepper
- 1 cup tightly packed kale, chopped
- ½ Tablespoon fresh sage, finely chopped
- ½ Tablespoon fresh thyme, chopped
- 4 cups Italian Bread or Sourdough, dried and cubed
- 6 ounces Gruyere cheese*, shredded, divided
- 1 egg, whisked
- ¾ cup vegetable stock, up to 1 cup
- Preheat oven to 400°F. Line a rimmed baking sheet with oven-safe cooling racks to prevent soggy mushroom bottoms. Make sure you wipe your mushrooms clean and remove the stems and gills.
- Place the mushrooms on the rack, top-side down, and sprinkle with salt. Bake for 10 minutes, then pour out the excess liquid and set the mushrooms aside.
- Meanwhile, make sure your bread is dried out and torn or cut into cubes. Place into a large mixing bowl.
- Heat a large skillet over medium heat and melt the butter. Add in the onion and celery; cook for 4-5 minutes. Add your salt and pepper – you want to do this in layers to add flavor. Add garlic and cook for an additional 1-2 minutes. Stir in kale and let cook for a minute or so until wilted. Remove from heat and stir in the fresh thyme and sage. Let cool slightly.
- Pour the onion mixture over the bread cubes, along with 1 cup shredded gruyere, and mix together. Add the beaten egg, stirring until combined. Add the vegetable stock, stirring and adding until the mixture is moist but not overly so.
- Place approximately 1 cup of stuffing in each mushroom cap, pressing down gently. Top with remaining shredded cheese. Cover loosely – I like to tent the foil so it doesn't stick to the cheese – and bake for 15 minutes. Remove the foil and bake for an additional 15-20 minutes until the top is golden brown and the edges of the stuffing are crispy.
- Serve immediately, garnishing with fresh herbs as desired. Enjoy!
- Do not rinse your mushrooms – be sure to wipe them clean with a towel.
- Easily double this recipe for a holiday dinner! I originally served it doubled.
- *Look for cheese specifically labeled vegetarian, if needed.
Disclaimer: The nutritional information provided for this recipe is only an estimate. The accuracy of the facts listed is not and cannot be guaranteed.