These delicious cheesy mushroom puff pastry tarts are a quick and elegant appetizer for any time of year, featuring caramelized onions, savory mushrooms, and sharp cheddar cheese, all layered on top of flaky puff pastry. These are the perfect handheld treat for the holidays, parties, gatherings, or an indulgent snack!

For more great appetizers, make sure you’ve tried my garlic breaded mushrooms recipe, or these dreamy French onion loaded potatoes.

Ingredient Notes

Here are a few notes on the ingredients you need for this recipe – scroll down to the recipe card for the exact ingredients list, quantities, and instructions.

• Mixed Mushrooms: I use chestnut and shiitake mushrooms in this recipe for depth of flavor, but feel free to use other types. Aim for two or more types of mushrooms to get maximum flavor from your tarts!
  
• Extra-Mature Cheddar Cheese: Opt for a strong cheddar to balance the sweetness of the caramelized onions and the umami of the mushrooms. Gruyere or blue cheese would be great choices (although if you’re vegetarian, make sure your cheese is labeled as suitable for vegetarians).
  
• Puff Pastry: Ready-made puff pastry makes this recipe easy and quick! I use a ready-made roll which comes with baking paper to make it super easy to transfer your puff pastry tarts to the oven,
  
• Balsamic Vinegar: A splash of balsamic adds sweetness and acidity to elevate the mushroom mixture, and pairs so perfectly with the caramelized onions and mushrooms!

Variations & Substitutions

• Vegan Option: Use vegan puff pastry, plant-based butter, and dairy-free cheese.
• Cheese Options: Swap cheddar for Gruyère, mozzarella, or goat cheese.
• Add Greens: Top the tarts with a handful of arugula or spinach just before serving.

How to Make These Cheese & Mushroom Puff Pastry Tarts

1. Caramelize the Onions

First, heat the oil in a pan over low heat, add the sliced onions, and sauté for 20–30 minutes until they’re beginning to turn caramelized. Stir occasionally to prevent burning.

2. Cook the Mushrooms

Add the butter, minced garlic, and mushrooms to the pan. Increase the heat to high and cook for 5–6 minutes, stirring occasionally, until the mushrooms are golden and their liquid has evaporated.

3. Season the Mixture

Stir in the balsamic vinegar and thyme and season with salt and pepper to taste. Remove from the heat and set aside – there should be very little liquid in the pan at this point! Continue cooking to evaporate the liquid to avoid soggy puff pastry tarts.

4. Prepare the Pastry

Unroll the puff pastry onto its baking paper. Cut it into approximately 8 rectangles, leaving a little space between each piece. 

5. Assemble the Tartlets

Sprinkle your grated cheddar cheese in the center of each rectangle, leaving a 1cm border around the edges – which makes it easier to hold and prevents the topping from spilling over. Top the cheese with the mushroom mixture, spreading it evenly over the cheese.

6. Bake the Tartlets

Brush the edges of each tartlet with the whisked egg for a golden finish. Bake in a preheated oven until the pastry is puffed and golden.

Remove the tartlets from the oven, sprinkle with fresh parsley, and serve warm.

Storage & Reheating

Store leftovers in an airtight container in the fridge for up to 2 days and reheat in a preheated oven at 180°C | 355°F for 5–7 minutes to restore crispness.

FAQs

Can I prepare these in advance? Yes, prepare the mushroom mixture and caramelized onions ahead of time. Store them in the fridge, then assemble and bake just before serving.

Can I freeze them? Yes! Freeze unbaked tartlets on a tray, then transfer them to a container or bag. Bake directly from frozen, adding an extra 5 minutes to the cooking time.