- 12 ounces cremini mushrooms, such as Baby Bella®
- 1/2 red onion, sliced vertically
- 1 tablespoon olive oil
- 1 tablespoon unsalted butter
- 2 tablespoons low-sodium soy sauce
- 1 teaspoon dried thyme
- 2 garlic cloves, minced
- salt and freshly ground black pepper to taste
- 1/2 (17.3 ounce) package frozen puff pastry, thawed
- 1 1/2 cups shredded Gruyere cheese
- 1 large egg, beaten
- 1 teaspoon dried thyme, or as needed for garnish (optional)
- Preheat the oven to 400 degrees F (200 degrees C). Line a baking sheet with parchment paper.
- Cut mushrooms into 1/4-inch-thick slices (don’t cut too thinly).
- Heat olive oil and butter in a large skillet over medium heat. Add mushrooms and onion and cook, stirring occasionally, until mushrooms are golden and onions are soft and translucent, 6 to 8 minutes.
- Stir in soy sauce, thyme, and garlic and cook until fragrant, 30 to 60 seconds. Season with salt and pepper; set aside.
- Unfold puff pastry sheet onto a lightly-floured work surface. Gently pat down or roll out dough with a rolling pin into a 10×10-inch square. Using a sharp knife, score a line about 1/2 inch from all edges to create a border, being careful not to cut all the way through. Use a fork to generously prick pastry sheet all over inside the border.
- Transfer puff pastry to the baking sheet, and brush the borders with beaten egg. Evenly spread Gruyere cheese inside the border, and top with mushroom mixture.
- Bake until tart is puffed and lightly browned, 10 to 12 minutes. Garnish with additional thyme, and serve warm.
If you’re unable to use Gruyere, Swiss cheese is a decent substitute, but won’t quite be as tasty as the Gruyere.
- Prep Time:15 mins
- Cook Time:20 mins
- Total Time:35 mins
- 414 Calories
- 30g Fat
- 23g Carbs
- 15g Protein