These stuffed portobello mushrooms are wonderfully flavorful and so pretty. They work well as an appetizer, or you can serve them as a tasty side dish.
The leftovers keep well in the fridge for several days, so sometimes I double the recipe and make a few extra mushrooms.
I love portobellos. They are tasty and substantial - almost meaty. I like their bold flavor and dense texture. I enjoy simply grilled portobello mushrooms, but stuffing them is especially tasty!
This recipe is lovely. The mushrooms are stuffed with a flavorful mixture of spinach, onions, garlic, and parmesan. They're delicious, pretty, and surprisingly easy to make.
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Ingredients
Here's an overview of the ingredients needed to make these stuffed portobello mushrooms. The exact measurements are listed in the recipe card below.
- Portobello mushrooms: Try to find mushrooms that aren't too shallow or deep. You want them to perfectly showcase the filling.
- Olive oil cooking spray: Spray is convenient, but you can simply brush the mushrooms with olive oil.
- Kosher salt and black pepper: I use kosher salt in most of my recipes. If using fine salt, you should use half the amount listed in the recipe card.
- Frozen chopped spinach: Frozen spinach is convenient, as I always have a bag in the freezer.
- Olive oil: For cooking the filling. You can use butter instead.
- Aromatics: Onion and garlic. While jarred minced garlic is acceptable, freshly minced garlic tastes better.
- Grated Parmesan: Use finely grated parmesan and not coarsely shredded.
Variations
- Sometimes I use butter instead of olive oil. Ghee works too, and I love the rich nutty flavor it adds.
- Add more seasonings to the spinach mixture. Good options I've tried and liked include dried oregano or thyme and a pinch of cumin.
- Sometimes I sprinkle the finished dish with red pepper flakes, as shown in the video below.
- Mix bacon bits into the spinach mixture. You can add them with the parmesan. It's really good!
Instructions
Making these stuffed portobello mushrooms is surprisingly easy. Scroll down to the recipe card for the details. Here are the basic steps:
Prep the mushrooms. You'll want to wipe them clean, then remove the stem and gills.
Pre-broil. Spray the mushrooms with olive oil, season them with salt and pepper, then briefly broil them.
Saute. Your next step is to defrost frozen chopped spinach, drain it well, and then saute it with onions and garlic in olive oil.
Stuff. Mix in parmesan, then stuff the mixture into the mushrooms.
Broil. Finish by broiling the mushrooms briefly, just until the filling is golden.
Expert Tips
Here are a few steps you can take to prevent the mushrooms from being soggy:
- Wipe clean, don't wash them - they absorb water.
- Scrape off their gills.
- Briefly broil the mushrooms to release some of their water content.
- In the final stage of broiling, broil briefly, just until the filling is browned. Broiling for too long will result in mushy mushrooms that have released their liquid into your filling.
- Thoroughly drain the defrosted spinach. You want no traces of water left! Place it in a colander and press on it repeatedly with the back of a large spoon until no water comes out.
If the finished dish is watery despite your efforts, you can still salvage it. Carefully drain the liquid, and place the mushrooms on paper towels to soak the extra liquid.
Recipe FAQs
They are the same species of mushroom but at different stages of maturity. White or button mushrooms are the youngest. Cremini mushrooms are older, and portobellos are the oldest. 
Yes. Scraping out the gills makes room for the filling, improves the mushrooms' texture, and helps reduce excess water.
The mushrooms will still release quite a bit of water as you broil them, so once they're done, place them upside down on paper towels to drain.
I prefer to wipe them clean with a damp paper towel. Mushrooms are porous; if you wash them, they'll absorb water and become soggy.
If you'd like to wash them, do so briefly, and dry them immediately.
Serving Suggestions
Stuffed portobello mushrooms make a great appetizer or side dish if you serve one per person.
When I serve them as a side dish, I like to pair them with one of the following entrees:
Or you can serve two per person with a couple of fried or poached eggs for a tasty and filling meatless meal.
Storing Leftovers
You can keep the leftovers in the fridge, in an airtight container, for 3-4 days. Place them on paper towels and replace the towels daily to absorb any extra liquid.
Reheat the leftovers in the microwave, covered, at 50% power. I don't recommend freezing the leftovers.
More Portobello Mushroom Recipes
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Recipe Card
Stuffed Portobello Mushrooms
Ingredients
- 4 portobello mushrooms
- Olive oil cooking spray
- 1 teaspoon Diamond Crystal kosher salt divided; or ½ teaspoon of any other salt
- ¼ teaspoon black pepper divided
- 10 oz frozen chopped spinach
- 2 tablespoons olive oil
- 1 onion small, finely chopped (6oz)
- 1 tablespoon fresh garlic minced
- ¼ cup Parmesan dry-grated
Instructions
- Preheat the broiler, setting the temperature to high (500°F). Set an oven rack in the middle of the oven. Line a broiler-safe, rimmed baking sheet with foil.
- Gently wipe the mushrooms clean with a damp paper towel. Twist or cut off the stem of each mushroom. Use a small spoon to scrape out the gills and discard them.
- Spray the mushroom caps with olive oil on both sides. Sprinkle them with ½ teaspoon kosher salt and ⅛ teaspoon black pepper. Broil until just tender, about 4 minutes per side. Place them upside down on paper towels to drain.
- Meanwhile, defrost the spinach in the microwave according to the directions on the package. Place the defrosted spinach in a colander to drain. Repeatedly press on the spinach with the back of a large spoon to remove as much water as possible.
- Heat the olive oil in a large skillet over medium heat. Add the onion and cook it for 5-7 minutes, stirring occasionally, until golden. Add the garlic, spinach, ½ teaspoon kosher salt, and ⅛ teaspoon black pepper. Cook, stirring, for 1-2 more minutes. Remove the skillet from the heat and allow it to cool for a couple of minutes, then mix in the Parmesan.
- Evenly distribute the spinach mixture among the mushrooms. Don't press down on the filling - it's prettier when piled high on top of the mushrooms. Place the stuffed mushrooms back under the broiler (on the middle rack) for 2-3 minutes, until the filling is golden. Serve immediately.
Video
Notes
- We're setting the oven rack in the middle of the oven because we don't want the mushrooms too close to the heating element.
- Scraping out the gills makes room for the filling, improves the mushroom's texture, and helps reduce excess water. The mushrooms will still release quite a bit of water as you broil them, so once they're done, place them upside down on paper towels to drain.
- I can't stress strongly enough how important it is to thoroughly drain the defrosted spinach. You want no traces of water left! So place it in a colander and press on it repeatedly with the back of a large spoon, until no water comes out.
- You can keep the leftovers in the fridge, in an airtight container, for 3-4 days. Place them on paper towels and replace the towels daily to absorb any extra liquid. Reheat the leftovers in the microwave, covered, at 50% power. I don't recommend freezing the leftovers.
Add Your Own Notes
Nutrition per Serving
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Vered DeLeeuw, LL.M., CNC, has been following a low-carb real-food diet and blogging about it since 2011. She's a Certified Nutrition Coach (NASM-CNC), has taken courses at the Harvard School of Public Health, and has earned a Nutrition and Healthy Living Certificate from Cornell University. Her work has appeared in several major media outlets, including Healthline, HuffPost, Today, Women's Health, Shape, and Country Living. 
Laura
Thank you for teaching me that I should broil the mushrooms to remove water! This worked so well. Delicious!
Vered DeLeeuw
You're very welcome, Laura!
KT
I enjoy portobello mushrooms, and had a spinach-stuffed recipe which I loved and made often about 15 years ago but lost track of it in a move. Yours is a really close match, thank you for sharing it! I did add some crumbled feta and sausage, and served them with grape tomatoes. Delicious!
Vered DeLeeuw
I love your additions! Sounds great.