If you want to make this vegan, choose a puff pastry such as Pepperidge Farm (which uses vegetable oils), and use a soy milk-based cream to seal the pastry.
Make Ahead: The roasted mushrooms and the prepared stuffing can be refrigerated for up to 5 days. The assembled Wellington can be refrigerated for up to 3 days before baking.
Roasted Portobello Mushroom, Pecan, and Chestnut Wellington
FOR THE MUSHROOMS
3—4 large portobello mushrooms (3/4 pound), stemmed
2 cloves garlic, sliced
1 tablespoon fresh thyme leaves
2 tablespoons fresh rosemary leaves
2 tablespoons extra-virgin olive oil
1/2 teaspoon fine sea salt
1/4 teaspoon freshly ground black pepper
FOR THE FILLING
1 tablespoon extra-virgin olive oil
1 large onion, thinly sliced
6 cloves garlic, coarsely chopped
1 tablespoon chopped fresh rosemary
1 teaspoon chopped fresh thyme
4 tablespoons rich red wine
1 teaspoon dark brown sugar
1 cup pecans
7 ounces cooked, peeled chestnuts (about 5/8 cup)
1-1/3 cups fresh white bread crumbs
2 teaspoons toasted sesame oil, plus more as needed
1 teaspoon fine sea salt, plus more as needed
14 ounces store-bought puff pastry dough (all-butter unless you are vegan), defrosted
2 tablespoons heavy cream (substitute soy cream for a vegan dish)
For the mushrooms—Preheat the oven to 350 degrees. Line a baking sheet with parchment paper.
Use a teaspoon to gently scrape off the dark gills from the underside of the portobello caps. Arrange the caps, gill side up, on the baking sheet; scatter with the garlic, thyme and rosemary; then drizzle with the olive oil. Sprinkle with the salt and pepper. Roast until the mushrooms are browned and tender but still holding their shape, 10 to 15 minutes. Let cool, then tip off and drain any collected liquid. Transfer the mushrooms to a plate.
Once the baking sheet itself cools, wipe it off and replace the parchment with a fresh piece of parchment paper.
For the filling—Heat the olive oil in a medium skillet over medium heat. Add the onion, garlic, rosemary and thyme. Reduce the heat to medium-low and cook, stirring frequently, until the onion is very soft and starting to brown, 15 minutes. Pour in the wine, and stir in the sugar until it has dissolved. Cook for another 2 to 3 minutes. Transfer the mixture to a large bowl.
Combine the pecans and chestnuts in a food processor; pulse until reduced to small pieces. Transfer to the bowl with the onion mixture, along with the bread crumbs, toasted sesame oil and salt.
Cut the mushrooms in half, and reserve all but one of the halves to form the center of your Wellington. Cut the remaining half into small chunks and add those to the bowl for the filling. Use your hands to thoroughly mix the filling. Taste, and add toasted sesame oil and/or salt as needed.
To assemble—Reheat the oven to 350 degrees. Lightly flour a large piece of parchment paper. Roll out the puff pastry dough on it to form a 10-by-14-inch rectangle that’s about 1/8 inch thick. Trim the edges of the dough to make it tidy; reserve the excess for decorating the top of the Wellington.
Spoon half of the filling mixture lengthwise down the center of the dough and spread it out evenly, leaving a border of 2 to 3 inches all around. Arrange the portobello halves evenly over the mixture down the middle of the dough, then cover with the remaining filling. (You may have more filling and/or mushrooms than you need; save them for another use.)
Brush the borders of the dough with a little cream. Fold over the ends and sides to wrap the dough around the filling. (Use the parchment paper to help if needed.) The dough should overlap in the middle; stretch it gently if needed. If there is a gap, use your excess dough to cover it, using cream to hold it in place. Use the parchment paper to lift the Wellington onto the prepared baking sheet, turning it over so the seam is on the bottom. Brush the dough with more cream and use the trimmings to make stars, leaves or other decorative shapes, and place them on the top, brushing them with cream.
To bake—Bake the Wellington until puffed, golden brown and heated through, 60 to 75 minutes. Let cool for at least 10 minutes. Cut into thick slices and serve warm or at room temperature.
Image: Scott Suchman for The Washington Post