INGREDIENTS

• 1 sheet puff pastry, defrosted and rolled out
• 2 tablespoons butter
• 1 tablespoon olive oil
• 1 onion, sliced
• 1 clove garlic, minced
• 4 cups cremini mushrooms, sliced
• 1 teaspoon dried thyme
• 1 tablespoon fig balsamic vinegar
• 1/2 cup white wine
• 1/2 cup heavy cream
• 5 ounces baby spinach
• 1 tablespoon Dijon mustard
• Salt and cracked pepper, to taste
• 1 cup Gruyère cheese, grated
• 1 egg, whisked

HOW TO MAKE IT

1. Preheat oven to 375°F.
2. Gently lay the rolled-out puff pastry into a STAUB skillet. Generously prick the pastry with a fork, including the overhang.
3. In a STAUB braiser, heat the olive oil and butter over medium-high heat. Once melted, add the onion and cook for several minutes until softened. Stir in the garlic and dried thyme and cook until fragrant, about 1 minute.
4. Add the mushrooms, cover, and cook for several minutes until they begin to soften. Stir in the balsamic vinegar and white wine. Bring to a simmer, then reduce the heat and cook until most of the liquid has evaporated.
5. Stir in the heavy cream and add the spinach. Cover and allow the spinach to wilt. Stir in the Dijon mustard and season with salt and cracked pepper to taste.
6. Remove from heat and let the mixture cool for 15 minutes.
7. Scatter one-third of the Gruyère cheese over the bottom of the prepared pastry. Spread the mushroom mixture evenly on top. Fold the edges of the pastry over the filling.
8. Brush the pastry with the whisked egg. Transfer to the oven and bake for 50–52 minutes, or until the pastry is golden brown.