Mushroom Crostini

This caramelized onion and mushroom crostini is a simple yet elegant hors d'oeuvres—perfect for when you want to impress your guests.

Three crostini topped with savory mushrooms and caramelized onions on a white plate.

Simply Recipes / Jessica Gavin

Crostini sounds fancy but it’s actually a very simple appetizer or snack to prepare. All you need is a crusty baguette to make crisp toasts that take 10 minutes to bake. The toasted bread is topped with a variety of flavorful ingredients.

These crostini provide guests with a delicious vegetarian option—caramelized onions, sautéed mushrooms, and herbed goat cheese. A savory and sweet combination of vegetables on top of a creamy spread and crunchy bread will disappear fast!

It’s a great option when you want to make plenty of servings with minimal effort. Plus, the topping options are endless. You can even prepare the components ahead of time, and assemble, serve, and enjoy whenever you want.

Toasting the Bread for Crostini

This is a two- to three-bite handheld starter. Slender baguettes are my top choice—they hold up well after toasting and have a light and crisp texture. Slice them about 1/2-inch thick and brush a high-quality extra virgin olive oil on both sides.

The oil crisps the bread when baked and adds a nice earthy and fruity flavor. It only takes about ten minutes to toast. The surface should be lightly browned but not completely dried out and brittle like croutons.

Three crostini topped with savory mushrooms and caramelized onions on a white plate.

Simply Recipes / Jessica Gavin

Why Caramelize Onions?

I like to caramelize the onions for a layer of flavor on the crostini. I add a small amount of brown sugar to kickstart the process of caramelizing the onions in olive oil and butter.

With a little bit of patience, the onions will soften, turn translucent, and then golden in color. The natural sugars in the vegetable come to the surface, adding a subtle sweetness. This extra effort makes a big flavor impact!

The Mushrooms

Brown mushrooms like cremini or baby bella are great for cooking because they hold their shape well, instead of shrinking into tiny pieces. I sauté them to concentrate their earthy, savory flavor.

Add a small amount of soy sauce to make the mushroom's flavor stronger. A splash of balsamic vinegar adds some acidity, which brightens the mushrooms and provides a hint of sweetness.

Mushroom and caramelized onion crostini on a white platter.

Simply Recipes / Jessica Gavin

Make a Creamy Goat Cheese Spread

To complement the tender slices of mushrooms and caramelized onions, make a tangy and creamy goat cheese spread. I like to keep this simple to not take away from the vegetable topping.

It has four ingredients: soft goat cheese, freshly chopped chives, and onion and garlic powder. That’s it! This also makes a nice dip for crackers, or I like to add some on top of soft scrambled eggs for breakfast.

How to Assemble the Crostini

Right before you’re ready to serve the crostini, shmear a thin layer of the goat cheese spread on top of the toast. The cheese also creates a barrier, so the toast doesn’t get soggy.

Add some of the warm mushrooms and onions on top, and garnish with freshly cracked black pepper and chopped chives. The toast tastes the best when enjoyed within an hour of topping.

Overhead view of crostini topped with savory mushrooms and caramelized onions on a white platter.

Simply Recipes / Jessica Gavin

Ingredient Swaps and Substitutions    

If you want to switch up the flavor profile of the crostini, try these mushroom, cheese, and herb options.

  • Use a mixture of mushrooms like brown, white, and dried porcini for a variety of mushroom flavors.
  • Goat cheese can be swapped for cream cheese, whipped feta, or mascarpone.
  • Add other fresh herbs to the cheese spread like chopped dill, basil, parsley, or oregano.

Storage Instructions

The toasts can be made up to five days in advance. Store them in an airtight container and leave them on the counter. You can freeze them for up to one month. Let them defrost on the kitchen counter before topping.

The crostini can be assembled up to two hours ahead of time and refrigerated until ready to serve. However, don’t wait any longer or the toast will turn soft!

Three crostini topped with savory mushrooms and caramelized onions on a white plate.

Simply Recipes / Jessica Gavin

More Handheld Apps to Try

Mushroom Crostini

Prep Time 25 mins
Cook Time 45 mins
Total Time 70 mins
Servings 6 servings
Yield 12 crostini

Ingredients

  • 1 (8-inch) baguette, cut into 12 1/2-inch slices
  • 3 tablespoons extra virgin olive oil, plus more for brushing
  • 1 tablespoon unsalted butter
  • 1/2 teaspoon brown sugar
  • 1/2 teaspoon kosher salt, divided
  • 2 medium (3 cups) yellow onion, sliced 1/4-inch thick
  • 8 ounces cremini or baby bella mushrooms, sliced 1/4-inch thick
  • 2 teaspoons minced garlic
  • 1 teaspoon balsamic vinegar
  • 1 teaspoon soy sauce
  • 1/4 teaspoon black pepper, plus more for garnish
  • 4 ounces goat cheese
  • 1 tablespoon sliced chives, plus more for garnish
  • 1/2 teaspoon garlic powder
  • 1/2 teaspoon onion powder

Method

  1. Preheat oven:

    Set the oven rack to the middle position. Heat oven to 350ºF.

  2. Toast bread slices in the oven:

    Using a pastry brush, brush both sides of the bread slices with 2 tablespoons of olive oil or more as needed. Arrange them in a single layer on a rimmed baking sheet.

    Bake until dry, lightly browned, and crisp, about 10 minutes. Flip the bread over halfway through baking. Cool on the baking sheet.

    Baking the toasts for mushroom, onion, and goat cheese crostini.

    Simply Recipes / Jessica Gavin

    Baking the toasts for mushroom, onion, and goat cheese crostini.

    Simply Recipes / Jessica Gavin

  3. Caramelize the onions:

    Heat a large skillet over medium-high heat. Add the remaining 1 tablespoon of olive oil, butter, brown sugar, and 1/4 teaspoon salt and stir to combine. Immediately add the onions and stir to coat.

    Cook, stirring frequently, until the onions begin to soften and lightly brown, about 5 minutes. Reduce the heat to medium heat, and cook the onions, stirring frequently, until caramelized, 10 to 12 minutes.

    Caramelizing onions for goat cheese crostini with mushrooms

    Simply Recipes / Jessica Gavin

  4. Sauté the mushrooms:

    Add the sliced mushrooms and cook until tender, stirring frequently, about 5 minutes.

    Add the garlic and sauté until fragrant, about 30 seconds.

    Add the balsamic vinegar, soy sauce, the remaining 1/4 teaspoon salt, and black pepper. Sauté for 1 minute. Season to taste with more salt and pepper. Set aside.

    Caramelized onions and mushrooms in a skillet to make goat cheese crostini with mushrooms.

    Simply Recipes / Jessica Gavin

  5. Mix cheese spread:

    In a medium bowl, combine the goat cheese, chives, garlic powder, and onion powder. Cover with plastic wrap and refrigerate if not using immediately.

    Mixing the cream cheese spread to make goat cheese crostini with mushrooms.

    Simply Recipes / Jessica Gavin

  6. Assemble the crostini:

    Using a butter knife, spread about 2 teaspoons of the goat cheese mixture over each slice of toasted bread.

    Top each with about 2 tablespoons of the caramelized onion and mushroom mixture. Sprinkle with black pepper and more chives, if you’d like. Arrange the crostini on a platter and serve.

    Close up of an overhead view of mushroom and caramelized onion crostini.

    Simply Recipes / Jessica Gavin