Herby Mushroom Stuffing Casserole Recipe (Vegetarian)

If your holiday season is marked by building anticipation over which dressing recipe will grace your Thanksgiving dinner, add this vegetarian mushroom stuffing casserole recipe to your list of holiday classics. It's rich, savory and full of all the holiday flavors you love.

Confession: I've been low-key obsessed with mushroom toast for a decade. Since I first tasted a slice of buttery grilled sourdough topped with a schmear of mascarpone and heaped with herbaceous shrooms...I just can't get enough. 

So when it was time to add some new thanksgiving recipes to my big day lineup, I decided to give traditional dressing a mushroom toast makeover. 

And here it is, friends. A creamy, garlicky, rich and herby bread stuffing, studded with mushrooms, shallots and mascarpone. 

Thanksgiving day, Christmas dinner and every special occasion you can create will be the perfect excuse to make this delicious side dish for everyone you love!

Ingredients for the best vegetarian stuffing with mushrooms and mascarpone:

Bread: sourdough bread is my preference for this vegetarian stuffing casserole. But any kind of bread with a bit of chew and texture will work. I've used French bread baguettes, thick, chewy slices of whole wheat bread, and even chunks of bagels. Aim to cut your bread into 2-inch cubes for the best texture. Use fresh bread or day-old bread. Either way, we bake the bread cubes in the oven to dry them out a bit before tossing them in our broth and mushroom mix, ensuring the bread soaks up every last drop of flavor.

Butter: you know salted butter is my jam, and that's what I use in this easy stuffing recipe. If using unsalted butter, taste the stuffing mixture BEFORE adding the eggs and add an extra pinch of salt, if needed. Remember the parmesan will add more salty flavor, too!

Veggies: mushrooms are the star of the show, and I used a combination of button and baby bellas. But you can go crazy with any combination that suits you! Supporting cast includes shallots and garlic. Substitute yellow onion, red onion or even scallions, if needed.

Herbs and spices: fresh parsley, thyme and sage add freshness and savory flavor to our homemade stuffing recipe. If you don't have fresh herbs, substitute 1 ¼ teaspoons dried poultry seasoning for the herbs. For spices, grab salt, black pepper and a pinch of red pepper flakes.

Broth: mushroom broth is ideal, but any kind of veggie broth works well. If you're cooking for meat eaters, use chicken broth or beef broth. 

Cheese: mascarpone adds the loveliest richness to our savory dressing, and parmesan adds nutty umami to the golden brown crust. Substitute gruyere, asiago or romano. 

Wine: white wine reduces quickly in our stuffing mixture and adds great flavor, complex and sophisticated. Omit if you prefer not to cook with wine. 

Eggs: eggs hold our very good stuffing together, adding richness and texture to the dish.

Step by step instructions for mushroom and mascarpone vegetarian stuffing recipe:

Preheat oven to 350°F. Spread the cubed bread on large rimmed baking sheet and transfer to the oven. Bake until bread is dry, about 10 minutes. Remove from the oven and set aside. 

Generously grease an 8x8 or similar baking dish. (To fill a 9x13 baking dish, double this recipe).

Meanwhile, melt butter in heavy large skillet over medium-high heat. Add mushrooms and shallots and sear until tender, about 5 minutes. 

Add the fresh herbs, garlic, salt, pepper and red pepper flakes to the vegetable mixture. Sauté for 2 minutes more.

Add white wine and let the wine condense for a minute. 

Remove the pan from heat and add about ⅓ cup mascarpone to pan (you should have about 2 tablespoons mascarpone remaining) and let it melt into the herby mushroom mixture. Combine the bread cubes with the mushroom mascarpone mixture.

Whisk the eggs and 1 ¼ cups cool broth in a large measuring cup. Add egg mixture to stuffing mixture and toss to coat.

Transfer the mixture to your greased baking dish. Scatter the remaining mascarpone across the top in pea-sized chunks, then sprinkle the with parmesan. 

Cover the casserole dish with aluminum foil. Bake 25 minutes. Remove foil. Bake until golden, about 20 additional minutes. For a crispy top, broil for the final 2 minutes.

Serve with crispy sage leaves. (To make, fry fresh sage leaves in a shallow pan of olive oil for a few seconds until crisp. Remove to a paper towel and sprinkle with salt).

FAQs and Serving Suggestions:

To store leftover stuffing, wrap tightly in plastic wrap and foil, or move to an airtight container, and store in refrigerator for up to 3 days. For reheating, warm in a skillet with a few tablespoons of stock and a pat of butter. Or, throw your mushroom stuffing in a greased waffle iron and watch the magic happen!

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