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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!
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!
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.
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.
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
Equipment
Ingredients
- 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
Instructions
- 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.2 tablespoon vegetable oil, 1 large onion, 4 ounce (113 g) baby bella mushrooms
- 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.2 tablespoon (28 g) unsalted butter, 1 1/2 granny smith apples, 1 teaspoon granulated sugar
- Add the cheese, chives, and thyme to the bowl and stir to combine the mixture well. Season with salt and pepper, to taste.1 1/2 ounce (43 g) grated gruyere cheese, 2 tablespoon chives, 1/2 teaspoon dried thyme
- 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.1 pound (907 g) package of frozen puff pastry, 1 egg
- 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!
I am hoping to make these for thanksgiving but I am heading to my sister in laws which is 2 hours away. I know that you mentioned that you can make the filling ahead of time – I wanted to find out when you state that you can also make the puffy pastry ahead of time, do you literally just cut it into squares and bake plain, and then once I reach my destination, assemble them by putting the filling on the already baked puffy pastry and reheat them so that they are warm. If this is correct, what would be the adjusted bake time? I am assuming that I would not need to bake them for the full 25 minutes if the puff pastry are already cooked or is that not correct? I am just not sure how much room she will have in her oven.
Hi yes, that’s exactly what I’m talking about! I would wrap the entire baking dish with foil so it doesn’t overcook/burn the puff pastry too much. You would probably just need to cook it for 10 minutes to warm it through. I’d microwave the filling a bit before you put it on the puff pastry to guarantee that the filling gets completely warmed through.
My husband hates mushrooms and I was wondering if there is another vegetable that could be substituted for this or if I left the mushroom out if it altogether, would it still be good?
It would still be just as good if you left out mushrooms.
can this recipe be made ahead of time? can it ne frozen
Yes, you can make this ahead of time. I would keep the topping separately from the puff pastry and assemble right before you serve. I haven’t ever tried freezing this so I’m not sure it would work.
which brand and type of gruyere cheese did you use?
I used a wegman’s type brand of gruyere and it was medium.
Do you roll out the puff pastry before cutting?
The puff pastry I get is folded into thirds so I just unfold it and cut. I don’t actually roll it out with a rolling pin.
HELP! Making these right now and just realized I thawed the puff pastry too long. I can’t speed at the sheets at all! Also just realized that it’s not a full pound which means I’ll need to buy more but I don’t think it will thaw in time! What do I do???
Hi, I’m sorry for the delay but I am not around all the time. I hope you were able to figure this out. If the puff pastry sheets weren’t able to be spread out/peeled off each other then you would have to start over with a new pack.
Do you really cook the onions for 30 minutes or is that a misprint?
To caramelize onions, you need to cook them for a long time :) it is not a misprint.
These look so delicious. Thank you for reposting this recipe.
I agree, adding a pork product would kick it up a notch. If one adds pieces of bacon on top before baking, is the bacon pre-cooked or are the pieces of bacon uncooked?
I assume cooked as there would be too much fat from the bacon as it cooks, but if it is cooked, does it not burn or get tough in the oven?
I would pre-cook the bacon then sprinkle the bacon on after the bites come out of the oven :)
Hi Julie, I have just looked over your fabulous recipe. My sister is hosting a high tea for our Mum’s 85th Birthday and I thought that your recipe would be perfect as one of the many things we will make to celebrate her 85th. It is foodies like yourself that make the world such a wonderful place to share recipes and enjoy life’s simple pleasures.
Thanks for such a sweet note, Barry. I hope you all enjoy this recipe and happy birthday to your mum!
What can I use instead of cheese?.
Hmm, I’m not quite sure. The gruyere really makes this dish have that distinct taste! Maybe just omit the cheese if you really don’t want it.