This caramelized onion and mushroom tart combines sweet onions, earthy mushrooms, and melted cheese on buttery puff pastry for a deliciously easy dish.
Fall is mushroom season, and this caramelized onion and mushroom tart is the perfect way to enjoy the season!
Why You’ll Love this Savory Tart
- Its loaded with mushrooms – I use shiitake and cremini mushrooms, but you can use any variety you like. Don’t be afraid to mix different types for more depth of flavor.
- Perfectly balanced flavors – Caramelized onions, mushrooms, and cheese create the perfect balance of sweet, earthy, and salty flavors. For cheese, try Gruyère, Grand Cru (similar to Gruyère), Fontina, or Asiago.
- Easy to make – This tart is simple to prepare using frozen puff pastry dough. I always use my favorite: the all-butter puff pastry from Trader Joe’s.
How to Make this Easy, Delicious Tart
Sauté the Mushrooms and Onions
- First, heat a skillet over medium heat without oil. Add the mushrooms and sauté for 5–6 minutes, or until tender and most of the moisture has evaporated. Once cooked, transfer them to a plate and set aside.
- Next, in the same skillet, add the olive oil and butter. When the butter melts, turn the heat to medium-high and add the onions.
- Sauté for about 5 minutes, stirring occasionally. Then, stir in the thyme leaves, reduce the heat to medium, and continue cooking for another 20 minutes, or until the onions turn golden and caramelized. Season with salt to taste. Once done, transfer the onions to a plate and let them cool slightly..
Assembling the Tart
- Meanwhile, on a well-floured surface, roll out the puff pastry dough into a rectangle. Carefully transfer it to a prepared baking sheet lined with parchment paper.
- Using a knife, score a ¾-inch border around the edges of the dough—be careful not to cut all the way through. Then, prick the center of the dough with a fork, leaving the border untouched.
- Now it’s time to build the tart: spread the caramelized onions evenly inside the border. Sprinkle half of the shredded cheese over the onions, then arrange the sautéed mushrooms on top. Add the remaining cheese and, if desired, garnish with a few thyme sprigs for color and aroma..
Baking Instructions
Brush the edges of the pastry with the egg wash, making sure to coat evenly for a golden finish. Next, bake the tart in a preheated 400°F oven for 18–20 minutes, or until the edges are puffed and golden brown.
Finally, remove the tart from the oven and let it cool for a few minutes before slicing. Serve warm and enjoy every flaky, flavorful bite!
Serving Ideas for Caramelized Onion and Mushroom Tart
This delicious, buttery tart can be served as an appetizer, side dish, main course, or even as a snack. It’s also a guaranteed hit for parties and casual get-togethers.
Don’t forget to serve it on your favorite fall-themed tableware pieces. One of my go-to favorites this time of year is Delamere from Spode. This collection, introduced in 2002, features the classic “British Flowers” border originally created by Spode in 1831. The intricate floral design is beautiful without feeling heavy, an elegant reflection of the craftsmanship Spode is known for.
More Delicious Puff Pastry Recipes
Caramelized Onions and Mushroom Tart
Ingredients
- 1 sweet onion thinly sliced
- 8 ounces cremini mushrooms cleaned, ends trimmed and sliced
- 4 ounces shiitake mushrooms cleaned, ends trimmed and sliced
- 1 tbsp fresh thyme leaves
- 1 tbsp olive oil
- 1 tbsp butter
- salt to taste
- 1 sheet frozen puff pastry thawed in fridge
- 1 egg for egg wash
- 1 cup shredded cheese (Gruyere, Grand Cru or your choice)
- 5-6 sprigs of thyme for garnish (optional)
Instructions
- Heat a skillet over medium heat (no oil). Add the mushrooms and sauté for 5–6 minutes, or until tender and moisture has evaporated. Transfer to a plate and set aside.
- In the same skillet, add olive oil and butter. Turn the heat to medium-high, add onions, and sauté for 5 minutes. Stir in the thyme leaves, then reduce heat to medium and continue cooking for about 20 minutes, stirring occasionally, until onions are caramelized. Season with salt to taste. Transfer to a plate and let cool.
- Preheat oven to 400° and line a baking sheet with parchment paper. On a well floured surface, roll out puff pastry dough into a rectangle and transfer it to the prepared baking sheet.
- Using a knife, score a ¾-inch border around the edges of the dough (be careful not to cut all the way through). Prick the center of the dough with a fork, leaving the border untouched.
- Spread the caramelized onions evenly inside the border. Sprinkle half of the shredded cheese on top, then arrange the sautéed mushrooms over the onions. Top with the remaining cheese and, if desired, garnish with a few thyme sprigs.
- Brush the edges of the pastry with the egg wash. Bake for 18–20 minutes, or until the tart edges are puffed and golden brown.
- Let the tart cool for a few minutes before slicing. Serve warm.