Mushroom Gruyere Puff Pastry Tart - A Savory, Buttery Crowd-Pleaser

Ingredients

• 1 sheet puff pastry, thawed
• 1 pound mixed mushrooms (cremini, shiitake, oyster), sliced
• 1 small yellow onion, thinly sliced
• 2 cloves garlic, minced
• 1 tablespoon fresh thyme leaves (or 1/2 teaspoon dried)
• 1 tablespoon unsalted butter
• 1 tablespoon olive oil
• 1/4 cup dry white wine or vegetable broth (optional, for deglazing)
• 3/4 cup grated Gruyere cheese
• 1/4 cup freshly grated Parmesan
• 1/4 cup crème fraîche or sour cream
• 1 teaspoon Dijon mustard
• Kosher salt and black pepper
• 1 egg, beaten (for egg wash)
• Optional garnish: chopped parsley or chives, a drizzle of balsamic glaze

Instructions

1. 1

   Preheat and prep: Heat the oven to 400°F (200°C). Line a baking sheet with parchment. Unfold the puff pastry and roll lightly to smooth the seams.

2. 2

   Score the border: With a knife, score a 1/2-inch border around the pastry (don’t cut through). Prick the center with a fork to prevent puffing.

3. 3

   Make the base: In a bowl, mix crème fraîche and Dijon with a pinch of salt and pepper. Spread over the center, keeping the border clean.

4. 4

   Sauté the mushrooms: Heat butter and olive oil in a large skillet over medium-high. Add mushrooms and let them sit for 2–3 minutes before stirring. Cook until they release liquid and it evaporates, 6–8 minutes.

5. 5

   Add aromatics: Stir in onion and cook until soft and lightly caramelized, 4–5 minutes. Add garlic and thyme; cook 30 seconds. Deglaze with wine or broth, scraping up browned bits. Season well.

6. 6

   Assemble: Sprinkle Gruyere and half the Parmesan over the crème fraîche base. Top with the mushroom mixture, spreading evenly. Brush the border with beaten egg and sprinkle remaining Parmesan on the edges.

7. 7

   Bake: Bake 20–25 minutes, until the pastry is puffed and deep golden and the cheese is melted.

8. 8

   Finish and serve: Rest 5 minutes. Garnish with parsley or chives and a light drizzle of balsamic glaze if you like. Slice and serve warm.