Mushroom Onion Cheese Pastry Recipe

Thaw and prepare pastry

Remove puff pastry sheets from the freezer and thaw according to package instructions (usually 30–40 minutes at room temperature). Lightly dust your work surface with the flour. Unfold each sheet and roll gently with a rolling pin to smooth seams and make roughly a 10 x 12-inch rectangle. Keep chilled while you make the filling.

Cook onion and mushrooms

Heat a large skillet over medium heat. Add the butter and olive oil. When butter melts and begins to foam, add the sliced onions and a pinch of salt. Sauté 6–8 minutes until onions are softened and starting to caramelize. Add the sliced mushrooms and increase heat slightly. Cook 6–8 minutes, stirring frequently, until mushrooms release their liquid and the liquid evaporates and the edges brown.

Add aromatics and deglaze

Stir in the minced garlic and thyme and cook 30–45 seconds until fragrant. Pour in the white wine or stock to deglaze the pan, scraping up any browned bits. Simmer 1–2 minutes until liquid has mostly reduced. Season with the remaining salt and black pepper. Remove the pan from heat and let the mixture cool 8–10 minutes.

Combine cheeses and filling

In a medium bowl, beat the softened cream cheese until smooth. Stir in the beaten egg (for filling) and the creme fraiche or sour cream if using. Fold in the grated Gruyère (or cheddar) and parmesan. Add the cooled mushroom-onion mixture and mix until evenly combined. Taste and adjust salt and pepper if needed. The filling should be moist but not soupy; if too wet, return to the pan briefly over low heat to evaporate more liquid and cool again.

Preheat oven and prepare baking sheet

Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.

Portion and fill pastries

Working with one puff pastry sheet at a time, cut each sheet into 6 equal rectangles (for 12 total smaller pastries) or 4 larger rectangles (for 8 pastries). Spoon about 2–3 tablespoons (for smaller) or 1/3–1/2 cup (for larger) of the mushroom-cheese filling onto the center of each rectangle, leaving a 1/2-inch border. Brush the border with a little of the egg wash to help seal.

Seal and score

Fold the pastry over the filling to make turnovers (triangles or rectangles) or simply fold edges over to create an enclosed parcel. Press edges firmly and crimp with a fork to seal. Alternatively, leave open-faced and fold a narrow border around the filling. If sealed, cut a small steam vent in the top of each pastry.

Egg wash and topping

Whisk the remaining egg for wash with 1 teaspoon water. Brush the tops and edges of each pastry with the egg wash. Sprinkle with sesame seeds or flaky sea salt if desired.

Bake

Bake on the prepared sheet in the preheated oven for 18–25 minutes (smaller pastries 18–20 min, larger 22–25 min) until golden brown and puffed. Rotate the sheet halfway through baking for even color. Remove from oven and let cool on the sheet for 5 minutes, then transfer to a wire rack to cool another 5–10 minutes before serving.

Serve warm or at room temperature. These pastries pair well with a simple green salad or a dollop of mustard or chutney.