In partnership withCalifornia Walnuts

Walnut-Stuffed Portobello Mushrooms Are the Definition of a Plant-Based Indulgence

published Apr 4, 2022
Walnut-Stuffed Portobello Mushrooms Recipe

A cheesy, nutty filling bakes in juicy portobello mushrooms until golden brown.

Serves4 to 6

Prep20 minutes to 25 minutes

Cook22 minutes to 27 minutes

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Credit: Photo: Christopher Broe; Food Stylist: Martha Tinkler

Whether you’re looking for more meatless Monday options or just trying to eat more plant-based meals in general, stuffed portobello mushrooms are a wonderful choice for something that is delicious and easy to pull off on a weeknight but still nice enough for a dinner party. To make them hearty enough to be a main dish, stuff them with a vegetarian blend of nutty walnuts, two kinds of cheese, herby chives, and breadcrumbs that bake up into a golden-brown filling.

When it comes to stuffing mushrooms for a main course, make sure the ingredients are both satisfying and filling. California walnuts are a great choice here because they add flavor and nutty texture, and are nutrient-dense and good for your heart.

Credit: Photo: Christopher Broe; Food Stylist: Martha Tinkler

Walnuts are wonderful for snacking and baking, but their versatility goes way beyond that. They’re also a great alternative to meat.

Credit: Photo: Christopher Broe; Food Stylist: Martha Tinkler

Making the Filling

A regular or mini food processor does most of the chopping for the filling, turning California walnuts and garlic into tiny pieces. If you don’t have a food processor, just finely chop everything by hand. Mix the walnuts and garlic with panko breadcrumbs, mozzarella cheese, Parmesan cheese, beaten egg, and chives. If you’d like a dash of heat, mix in some red pepper flakes, too.

Credit: Photo: Christopher Broe; Food Stylist: Martha Tinkler

Pro Tip: Roast the Mushrooms Twice

Portobello mushrooms contain a lot of water, so roasting them twice helps cook off some of it and keeps the filling from getting soggy. Start by scraping out the gills of the mushrooms, then roast the portobellos for 10–12 minutes on their own first. Soak up any moisture on the mushrooms and baking sheet with paper towels, stuff the mushrooms caps, and roast again until the filling is browned.

Serve these walnut-stuffed portobello mushrooms with a side salad, glazed baby carrots, or sautéed asparagus for a peak summer meal.

Walnut-Stuffed Portobello Mushrooms Recipe

A cheesy, nutty filling bakes in juicy portobello mushrooms until golden brown.

Prep time 20 minutes to 25 minutes

Cook time 22 minutes to 27 minutes

Serves 4 to 6

Nutritional Info

Ingredients

  • 4

    (5-inch) large or 6 (4-inch) medium portobello mushrooms

  • 3 tablespoons

    olive oil, divided

  • 3/4 teaspoon

    kosher salt, divided

  • 1/4 teaspoon

    freshly ground black pepper

  • 1

    large egg

  • 2 cloves

    garlic

  • 1 cup

    raw California walnuts

  • 4 ounces

    low-moisture mozzarella cheese, shredded (about 1 cup)

  • 1/2 ounces

    Parmesan cheese (3 tablespoons freshly grated or 2 tablespoons store-bought grated)

  • 1 small bunch

    fresh chives

  • 1/2 cup

    panko breadcrumbs

  • 1/4 teaspoon

    red pepper flakes (optional)

Instructions

  1. Arrange a rack in the top third of the oven and heat the oven to 400ºF. Line a rimmed baking sheet with parchment paper.

  2. Remove the stems from 4 large or 6 medium portobello mushrooms. Use a spoon to gently scrape out and discard the mushroom gills to make room for the stuffing. Brush the mushrooms all over with 2 tablespoons of the olive oil, then season all over with 1/2 teaspoon of the kosher salt and 1/4 teaspoon of the black pepper.

  3. Place the mushrooms on the baking sheet stem side down. Roast for 10 minutes for medium mushrooms, 12 minutes for large. Meanwhile, make the filling.

  4. Place 1 large egg in a medium bowl and beat lightly with a fork. Coarsely chop 2 garlic cloves and place in a regular or mini food processor fitted with the blade attachment. Add 1 cup raw California walnuts and pulse until chopped into pieces no larger than a peppercorn, 15 to 25 (1-second) pulses. (Alternatively, finely chop both by hand.) Add to the bowl with the egg.

  5. Prepare the following, adding each ingredient to the bowl as you complete it: Grate 4 ounces mozzarella cheese on the large holes of a box grater (about 1 cup). Grate 1/2 ounce Parmesan cheese on the smaller holes of a box grater (about 3 tablespoons), or use 2 tablespoons store-bought grated. Finely chop 1 small bunch fresh chives until you have 1/4 cup; reserve 1 tablespoon for garnish and add the remaining to the bowl.

  6. Add the remaining 1 tablespoon olive oil, remaining 1/4 teaspoon kosher salt, 1/2 cup panko breadcrumbs, and 1/4 teaspoon red pepper flakes. Stir until evenly combined and moistened.

  7. When the mushrooms are ready, remove the baking sheet from the oven. Flip the mushrooms and use paper towels to blot up the excess moisture from the mushrooms and baking sheet. Stuff the mushrooms with the filling.

  8. Return the baking sheet to the oven and roast until the mushrooms are tender and the filling is browned in spots, 10 to 15 minutes. Garnish with the reserved chives.

Recipe Notes

Storage: Leftovers can be refrigerated in an airtight container for up to 4 days.