Ingredients

• 2 tablespoons butter

• 2 shallots or 1 medium onion

• 2 teaspoons dried thyme

• 1 clove garlic

• 1 tablespoon oil

• 14 oz (400g) mushrooms (mix of cremini, white button, shitake, etc.)

• 1 tablespoon balsamic vinegar

• 2 tablespoons dry white wine

• salt and pepper to taste

• 1 1/4 cups (125g) shredded Gruyere cheese

• 1 sheet puff pastry about 9-10 ounce (270g)

• 1 egg for brushing the edges

 

Instructions

Cook the mushrooms:

1. Preheat the oven to 375°F –no convection. Cut the mushrooms into 1/4-1/3 inch (5-7mm) slices. Leave small mushrooms whole, cut medium mushrooms into 2 parts, and large mushrooms into 3-4 parts. Don't cut the mushroom too thinly.

2. Cut the shallot into slices, finely chop the garlic.

3. Heat butter in a large frying pan over medium-low heat. When hot add the onions and thyme, cook for a couple of minutes, until the onion is soft. Add the garlic and cook for 30 seconds, stirring.

4. Transfer the onions with garlic to a plate.

5. Add oil to the pan and increase the heat to the highest setting. Add mushrooms in an even layer, starting with button mushrooms. Cook without stirring for 1-2 minutes then add the vinegar and cook, stirring, for about 4-8 minutes (depending on how powerful your stovetop is) until the mushrooms have reduced their volume in half and all the liquid is evaporated. Don't stir the mushrooms for about a minute when almost all liquid is evaporated, letting the mushrooms brown a little.

6. Add white wine and cook until all liquid is evaporated.

7. Add the onions with garlic back to the pan, stir with the mushrooms. Season the mushrooms and onions with salt and pepper. Transfer to a plate and leave to cool slightly.

 

Assemble and bake the tart:

1. Take the puff pastry out of the fridge. With a tip of a sharp knife, score through the top layers of the puff pastry by running the knife along all four sides of the dough (leaving about 1-inch / 2.5 cm border). Do not cut all the way through the dough. Transfer the pastry, along with the parchment paper that comes with it to a baking sheet. Prick the dough (but not the borders) with a fork.

2. Sprinkle the cheese in an even layer over the dough.

3. Top with cooled mushrooms and onions.

4. Brush the edges of the tart with beaten egg. Prick the dough with a fork a couple times more (or it will puff up in the oven), not the edges, just the center of the tart.

5. Bake the tart for about 20-25 minutes or until golden.

6. Enjoy!

 

Notes

• Ingredient notes:

  • Puff pastry - all-butter puff pastry tastes best so choose that if you can find it

  • Mushrooms - any kind will work here

  • Shallots - you can also use onions

  • Thyme - fresh or dried, you could also use French or Italian herbs

  • Balsamic vinegar - if you don‘t have it on hand, you can omit it or add 1/2 Tbsp of soy sauce instead

  • White wine-any kind will work here

  • Egg - you can use heavy cream or milk to brush the edges of the tart

  • Cheese - it‘s important to use a flavorful cheese like Gruyere cheese, Appenzeller cheese (or other Alpine-style full-bodied cheese), sharp aged cheddar would also work

• Serving suggestion: I like to serve this tart as an appetizer with a side of some salad greens and tomatoes. It‘s quite rich so you want to serve it with something light and crunchy. A crisp dry white wine would also be a lovely addition.

• You could also cut the dough into small squares or circles and make small individual tartlets.

• Storage: This mushroom tart tastes best freshly made (especially slightly warm) or 1-2 hours after baking. After this time it won‘t be crunchy anymore and the pastry will become a bit soggy. It‘s still very tasty, though! You can reheat it in a microwave or in an oven until warm.

• It's important to take the puff pastry out of the fridge when you have all the other ingredients ready. It will be sticky when warm.