Golden Mozzarella Stuffed Portobello Sandwiches with Smoky Mustard Sauce

These hearty portobello mushroom sandwiches are a vegetarian dream. The mushrooms are stuffed with gooey mozzarella and a crunchy panko topping, then roasted until tender and golden. Served on soft brioche buns with a tangy smoky mustard spread, they’re balanced by a side of ranch-dressed mixed greens.

This recipe comes together quickly with minimal prep-just stuff, bake and assemble. Perfect for a weeknight dinner that feels special without the fuss.

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Ingredients

4 ounce BaconView ingredient guideLike ingredientDislike ingredient

0.5 cup Panko BreadcrumbsView ingredient guideLike ingredientDislike ingredient

1 tablespoon Fry SeasoningView ingredient guideLike ingredientDislike ingredient

1 unit Oven-Ready TrayView ingredient guideLike ingredientDislike ingredient

2 ounce Smoky MustardView ingredient guideLike ingredientDislike ingredient

4 ounce Mixed GreensView ingredient guideLike ingredientDislike ingredient

0.5 cup Mozzarella CheeseView ingredient guideLike ingredientDislike ingredient

2 tablespoon MayonnaiseView ingredient guideLike ingredientDislike ingredient

2 unit Brioche BunsView ingredient guideLike ingredientDislike ingredient

1 unit TomatoView ingredient guideLike ingredientDislike ingredient

1 unit Crispy Fried OnionsView ingredient guideLike ingredientDislike ingredient

3 ounce Buttermilk Ranch DressingView ingredient guideLike ingredientDislike ingredient

2 unit Portobello MushroomsView ingredient guideLike ingredientDislike ingredient

4 teaspoon (tsp) Olive OilView ingredient guideLike ingredientDislike ingredient

teaspoon (tsp) SaltView ingredient guideLike ingredientDislike ingredient

teaspoon (tsp) Black PepperView ingredient guideLike ingredientDislike ingredient

Instructions

1. Adjust rack to top position and preheat oven to 425°F. Wash and dry produce. Using a spoon, scrape out and discard the black gills from the underside of each portobello mushroom; trim any large stems. Slice the tomato into ¼-inch-thick rounds.
2. Drizzle both sides of each mushroom with 2 teaspoons olive oil; rub to coat evenly. Season with half the Fry Seasoning, salt and pepper. Place mushrooms top-side down in the oven-ready tray. Sprinkle mozzarella evenly over the mushrooms.
3. In a small bowl, combine panko, remaining Fry Seasoning, a drizzle of olive oil, salt and pepper. Sprinkle the panko mixture over the mushrooms, pressing lightly to adhere. Tightly cover the tray with aluminum foil.
4. Bake on the top rack until mushrooms are tender, 14-16 minutes. Remove foil and continue baking until the cheese and panko are golden brown, about 5 minutes more. Watch carefully to avoid burning.
5. While mushrooms bake, in another small bowl, mix mayonnaise and smoky mustard. Halve and toast the brioche buns. In a large bowl, toss mixed greens with half the ranch dressing; season with salt and pepper.
6. Spread the cut sides of the buns with the smoky mustard sauce. Fill each bun with sliced tomato, a stuffed mushroom and crispy fried onions. Divide sandwiches and salad between plates. Drizzle remaining ranch dressing over the salad if desired. Serve immediately.

Recipe Tips

FAQ

Can I use a different type of mushroom?

Portobellos are best for their meaty texture and size, but large cremini mushrooms can work in a pinch.

How do I make this recipe dairy-free?

Use dairy-free mozzarella and ranch dressing and skip the brioche buns or use vegan buns.

Can I prepare the mushrooms ahead of time?

You can stuff the mushrooms and refrigerate them up to a day in advance. Bake just before serving.