Portobello Stuffed Mushrooms

A close-up of a stuffed portobello mushroom topped with melted cheese, spinach, herbs, and breadcrumbs, served on a rustic ceramic plate with fresh chopped parsley sprinkled around.

Portobello Stuffed Mushrooms

These baked Portobello Stuffed Mushrooms are my go-to when I want something that tastes restaurant-quality but still works for a weeknight dinner. Each meaty mushroom cap is loaded with a savory filling of spinach, garlic, Gruyère, Parmesan, and breadcrumbs, then baked until golden and bubbly.

Course Appetizer, Side Dish

Cuisine American

Keyword stuffed portobello mushrooms

Prep Time 15

Cook Time 30

Total Time 45

Servings

Calories 237kcal

Author Julia

Ingredients

4 large Portobello mushrooms
2 tablespoons olive oil
½ small onion finely diced
2 cloves garlic minced
2 sprigs fresh thyme stalks removed
2 cups fresh spinach chopped
½ cup breadcrumbs
½ cup Gruyère cheese shredded
¼ cup Parmesan cheese grated
2 tablespoons fresh parsley finely chopped
salt and pepper to taste

US Customary - Metric

Instructions

Pre-Cook Mushrooms

Preheat the oven to 375ºF. Line a baking sheet with parchment paper and set aside.
Wipe the mushrooms clean with a damp paper towel. Remove the stalks from the mushrooms, finely chop them and save for later. Scrape the gills from inside the mushrooms and discard.
Place the mushrooms on the baking sheet, open side up. Cook in the oven for 15 minutes after which time the mushrooms will have expelled some water/juice which can be reserved for later.

Make the Filling

Place a skillet or cast iron dish over a medium heat, and add the oil. When the oil is hot add the onion and sauté for about 2 minutes until soft, then add the garlic, chopped mushroom stalks and thyme, then cook for another minute.
Stir in the chopped spinach and juice from the cooked mushrooms. Cook for 1-2 minutes until the spinach has wilted then remove from the heat.
To the dish, add the breadcrumbs, Gruyère and Parmesan. Season with salt and pepper and mix until well combined.

Assemble & Bake

Divide the mixture between the mushrooms, pressing it down gently into the caps.
Bake for 15-20 minutes, or until the mushrooms are tender, the cheese is melted and the the tops are golden.
Scatter over the chopped parsley, a few extra thyme leaves and a little extra parmesan to serve.
Note: I provide helpful step-by-step photos below this recipe card. ⬇️⬇️

Notes

For extra crunch, mix two tablespoons of breadcrumbs with two tablespoons of Parmesan and sprinkle over the mushrooms before baking.
If you’d like some heat, stir in red pepper flakes with the filling. You could also enhance the texture by adding ¼ cup of chopped nuts, such as walnuts or hazelnuts.
Finish with a quick broil (optional but amazing): If your tops aren’t golden enough, a 1–2 minute broil gives that crisp, bubbly finish. Watch closely!
Why are my stuffed mushrooms watery? Usually, it’s one of three things: the caps weren’t pre-baked long enough, the spinach/onion mixture wasn’t cooked down, or the mushrooms were rinsed/soaked. Wipe mushrooms dry with paper towels, pre-bake, and drain. Sauté the filling until it looks “dry-ish” before adding cheese and crumbs.
Can I make these gluten-free? Yes. You can swap in gluten-free breadcrumbs or crushed gluten-free crackers. Panko-style GF crumbs also work great.
Can I make these ahead of time? Yes. You can make the filling up to 2 days ahead and store it covered in the fridge. You can also par-bake the caps, cool them, and refrigerate overnight. When you're ready to serve, stuff and bake for 15-20 minutes. If assembling fully ahead, refrigerate for up to 24 hours and add a few extra minutes to the bake time.

Storage Tips

Fridge: Let the stuffed portobello mushrooms cool completely, then store them in an airtight container in the refrigerator for up to 3 days.
Freezing: I don't recommend it as the mushrooms tend to release a lot of water after freezing and thawing, which can make the caps and filling soft and soggy.
Reheating: Place mushrooms on a baking sheet and warm in a 350ºF oven for 10–15 minutes, until heated through and the tops are lightly crisp again.

Nutrition