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Caramelized Onion, Mushroom, Apple and Gruyere Bites

4.43 from 19 votes
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This caramelized onion, mushroom, apple and gruyere puff pastry appetizer recipe is a must-make starter for Thanksgiving—or really for any party. No one can resist flaky, buttery puff pastry, especially when it’s topped with melty cheese and sweet onions!

Overhead shot of Caramelized Onion, Mushroom, Apple, and Gruyere Puff Pastry Appetizer

These puff pastry appetizer bites look elegant and time-consuming, but sometimes looks can be deceiving. I’m all about simple elegance and these apps fit the bill. I don’t want to be tucked away in the kitchen for two hours on one dish, especially when I have guests over. This recipe is easy enough that you can make it for Thanksgiving and still have time for making all your sides and desserts!

The caramelized onions give this appetizer a touch of sweetness, but when paired with the sautéed mushrooms and tart apple, you get the perfect contrast in flavors. Combined with the buttery puff pastry and earthy gruyere, you have yourself a perfect appetizer that everyone will love.

What You’ll Need

Here’s a rundown of what you’ll need to make this crowd-pleasing puff pastry appetizer.

  • Vegetable oil – Olive oil will work, too.
  • Onion – Yellow onions are best for caramelizing.
  • Baby Bella mushrooms – If you can’t find these, you can use white mushrooms instead.
  • Unsalted butter
  • Granny Smith apples – You can use other apple varities as well. I prefer the tartness of Granny Smiths but your favorite kind of apple will work just fine!
  • Granulated sugar
  • Gruyere cheese – If you prefer to use a different kind of cheese I suggest something earthy and nutty, like Asiago, Emmentaler, or Dubliner.
  • Chives
  • Dried thyme
  • Puff pastry
  • Egg – This will be used to make an egg wash that gives these puff pastry appetizers their golden hue.

Can I add bacon to this recipe?

Adding chopped bacon on top would make these puff pastry appetizer bites even more enticing. I would add the bacon to the filling mixture and stir it together. Three or four slices of bacon, chopped up, would be great!

Closeup shot of Caramelized Onion, Mushroom, Apple, and Gruyere Puff Pastry Appetizers

How to Make Caramelized Onion, Mushroom, Apple, and Gruyere Bites

Once you make the filling, assembling these puff pastry appetizers is a cinch. Here’s a step-by-step guide:

Prepare. Preheat your oven to 400ºF and line two baking sheets with parchment paper or silicone baking mats.

Caramelize the onions. Heat the oil in a large skillet over low heat, then add the onions and a teaspoon of salt. Cook for about 30 minutes, or until the onions are jammy and nicely browned. Transfer to a bowl and set aside. 

Cook the mushrooms. Return the skillet to the heat and sauté the mushrooms until they’re tender, or about 5 minutes. Transfer the mushrooms to the bowl with the onions.

Cook the apples. Return the skillet to the stovetop again and add the apples and sugar. Cook until the apples are tender, or about 10 minutes. Add the cooked apples to the bowl with the onions and mushrooms.

Combine the filling ingredients. Add the cheese, chives, and thyme to the bowl with the onions, mushrooms, and apples. Stir to combine and season with salt and pepper to taste.

Prepare the puff pastry. Use a pizza cutter to cut the puff pastry into 2-inch squares. Place the squares on the baking sheets and use a pastry brush to coat the tops with beaten egg. Place a tablespoon of the filling mixture onto each puff pastry appetizer.

Bake. Place the baking sheets in the oven and bake the gruyere bites for 25 minutes, rotating the pans halfway through the cooking time. The bites are done when the puff pastry is golden brown and crisp.

Serve. Let the bites cool slightly, then serve them to your guests.

Closeup shot of Caramelized Onion, Mushroom, Apple, and Gruyere Bites

Tips for Success

Here are some tips to help you make sure this puff pastry appetizer recipe turns out perfect!

  • Caramelize the onions. That means cooking them low and slow. There are a lot of recipes for caramelized onions online that will have you cooking the onions at a higher temperature for a shorter amount of time, but this isn’t caramelizing—it’s sautéing. If you want your onions jammy and sweet, it’s going to take at least 30 minutes, or maybe even longer, depending on your stove.
  • Don’t forget to thaw the puff pastry. There’s really no good way to do it quickly if you forget about it, so put an alarm on your phone to help you remember if you have to. Defrost it in the fridge (not at room temperature!) for about 4 hours.
  • Stick with Granny Smith apples. In a baking recipe, there are usually a number of different types of apples you can use, but this puff pastry appetizer recipe really depends upon the tartness of Granny Smiths.

Can I Make These Ahead of Time?

You can prep the filling ahead of time, but don’t put it on the puff pastry. All the liquid from the filling will make the puff pastry soggy and not puffy.

To make these ahead, prepare the filling and refrigerate it up to 2 days in advance. When you are ready to bake these you’ll follow the recipe exactly as written—thaw the puff pastry, cut it, place the topping onto each of the squares, then bake them as instructed.

Closeup shot of Caramelized Onion, Mushroom, Apple, and Gruyere Puff Pastry Appetizers garnished with fresh chives

Don’t miss me making this caramelized onion, mushroom, apple, and gruyere puff pastry appetizer in the video below!

More appetizer and snack ideas:

Caramelized Onion, Mushroom, Apple & Gruyere Bites

You must add these caramelized onion, mushroom, apple, & gruyere bites to your Thanksgiving appetizer list.
4.43 from 19 votes
Prep Time: 10 minutes
Cook Time: 1 hour 5 minutes
Total Time: 1 hour 15 minutes
Servings: 30 bites
Author: Julie Chiou
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  • 2 tablespoon vegetable oil
  • 1 large onion, thinly sliced
  • 4 ounce (113 g) baby bella mushrooms, sliced
  • 2 tablespoon (28 g) unsalted butter
  • 1 ½ granny smith apples, cubed into 1/2-inch cubes
  • 1 teaspoon granulated sugar
  • 1 ½ ounce (43 g) grated gruyere cheese
  • 2 tablespoon chives, minced
  • ½ teaspoon dried thyme
  • 1 pound (907 g) package of frozen puff pastry, thawed
  • 1 egg, beaten


  • Preheat oven to 400 °F (204 °C). Line baking sheets with silicone baking mats. Set side.
  • In a large skillet, heat the vegetable oil and cook the onions (with 1 tsp. of salt) until they’re golden brown, about 30 minutes. Remove and set aside in a large bowl. In the same skillet, sauté mushrooms until tender, about 5 minutes. Remove and set aside in the bowl with the onions.
  • In the same skillet, melt the butter and add in the apples with the sugar. Cook until softened, about 10 minutes. Remove from pan and add to the large bowl with onions and mushrooms.
  • Add the cheese, chives, and thyme to the bowl and stir to combine the mixture well. Season with salt and pepper, to taste.
  • With a pizza cutter, cut the puff pastry into 2-inch squares and place them on the lined baking sheets. Using a pastry brush, brush beaten egg on the squares.
  • Using a tablespoon, place filling in the middle of each puff pastry.
  • Bake for 25 minutes, rotating the pans halfway through and switching the baking sheet on the top rack to the bottom and the bottom to the top, until the pastry is golden brown and crisp.
  • Let the tarts cool a bit before serving, you don’t want people to burn the roofs of their mouths!


Recipe Notes


Serving: 2 “bites” | Calories: 240 kcal | Carbohydrates: 18 g | Protein: 6 g | Fat: 16 g | Fiber: 2 g | Sugar: 4 g

This website provides approximate nutrition information for convenience and as a courtesy only. Nutrition information can vary for a variety of reasons. For the most precise nutritional data use your preferred nutrition calculator based on the actual ingredients you used in the recipe.

The default measuring system for this website is US Customary. Unit conversions are provided for convenience and as a courtesy only. While we strive to provide accurate unit conversions, please be aware that there may be some discrepancies.

Recipe Rating


Wednesday 23rd of November 2022

This recipe is fantastic! It does take a while for the prepping though (Four hours for thawing the pastry, cooking each main ingredient separately....) Please do NOT use phyllo dough. It will not turn out well. Ask me how I know......


Monday 27th of January 2020

Made these delicious little tarts as part of my appetizer selection for a brunch. They were a huge hit. I’m preparing for another brunch so I’m about to make them again!! These are definitely on my “go to” list!


Wednesday 27th of November 2019

Are you sure it’s 1.5 oz if cheese? Doesn’t sound like enough.

Julie Wampler

Thursday 28th of November 2019

You can use more if you want!


Monday 12th of November 2018

how long to bake if I make one large tart instead

Julie Wampler

Monday 12th of November 2018

I would bake the same amount of time.


Monday 12th of November 2018

I need these... like... now. I (sadly) have never used puff pastry, even though I love it. Wondering if I might be able to use a maple leafs cut-out for the pastry, or if the dough is too delicate to where it may burn on the skinnier end pieces. Thoughts?

Julie Wampler

Monday 12th of November 2018

Those would be so pretty! You could maybe do it and then tent with foil if you see that they're getting to brown?