2 sheets frozen puff pastry dough from a 17.3 ounce package
All-purpose flour for dusting
1 large egg beaten with 2 teaspoons of water
3 tablespoons extra-virgin olive oil
2 shallots finely minced
1 pound assorted wild and cultivated mushrooms (such as cremini, shiitake, and chanterelle) wiped or brushed clean, stems trimmed, finely chopped
1 1/2 teaspoons kosher or sea salt
Freshly ground pepper
2 tablespoons fresh flat-leaf parsley minced
1 tablespoon fresh dill minced
1 teaspoon fresh thyme leaves minced
1/4 cup goat cheese at room temperature
"To make the mushroom filling, in a large skillet over medium-high heat, warm the olive oil and swirl to coat the pan. Add the shallots and sauté until just beginning to soften, about 2 minutes. Add the mushrooms and sauté, stirring frequently, until they just begin to soften, about 3 minutes. Add the salt and a few grinds of pepper and continue to sauté until the mushrooms give off their juices, about 5 minutes longer. Add the parsley, dill, thyme, and goat cheese to the pan. Sauté, stirring constantly, until the liquids are almost evaporated and the goat cheese is blended in, 1 to 2 minutes longer. Remove from the heat. Set aside to cool.
Position one rack in the center and another one in the lower-third of the oven. Preheat the oven to 425°F. Have ready two rimmed baking sheets, preferably nonstick. For pans without a nonstick finish, line the pans with parchment paper or use silpat mats.
Working with one pastry sheet at a time, unfold the pastry sheet and place it on a lightly floured cutting board. Using a rolling pin, roll the pastry just enough to remove the fold marks, and then continue to roll to a 10-by-15-inch rectangle. Using a sharp knife or pizza wheel, cut the pastry sheet lengthwise into four 2 1/2-by-15-inch strips. Cut each strip evenly into six pieces to form a total of twenty-four 2 1/2-inch squares. Repeat with the second sheet of pastry.
Brush each square with egg wash on the side facing up. Put a rounded teaspoon of filling in the center of each square. Gather the four corners and bring them up to the center, pinching the dough together firmly to secure it at the point, forming square pouches. Leave the seams along the edges open so some of the mushroom filling shows. Transfer the mushroom pockets to the baking sheets placing them about 1 inch apart. Lightly dab the sides of the pockets with any remaining egg wash.
Bake the mushroom pockets for 10 minutes, switch the position of the baking sheets, and continue to bake until puffed, golden brown on the sides and bottom, and crisp, about 4 to 6 minutes longer. Transfer to a rack to cool slightly. Serve warm or at room temperature.
Do ahead: The mushroom filling can be cooled, covered, and refrigerated for up to 3 days. Remove the filling from the refrigerator 1 hour before filling the pastry pockets to soften it slightly. The mushroom pockets can be made and assembled completely and frozen, unbaked. Freeze the unbaked pastries on rimmed baking sheets, and then transfer them to a freezer container, arranging the pockets in layers between sheets of waxed paper. The pastries can be frozen for up to 1 month. Bake the pockets without thawing first; the baking times will be longer, about 20 to 25 minutes so follow the recipe’s doneness cues."