Step 1

1 For the mushrooms: Preheat the oven to 350 degrees

Step 2

2 Line a baking sheet with parchment paper

Step 3

3 Use a teaspoon to gently scrape off the dark gills from the underside of the portobello caps

Step 4

4 Arrange the caps, gill side up, on the baking sheet; scatter with the garlic, thyme and rosemary; then drizzle with the olive oil

Step 5

5 Sprinkle with the salt and pepper

Step 6

6 Roast until the mushrooms are browned and tender but still holding their shape, 10 to 15 minutes

Step 7

7 Let cool, then tip off and drain any collected liquid

Step 8

8 Transfer the mushrooms to a plate

Step 9

9 Once the baking sheet itself cools, wipe it off and replace the parchment with a fresh piece of parchment paper

Step 10

10 For the filling: Heat the olive oil in a medium skillet over medium heat

Step 11

11 Add the onion, garlic, rosemary and thyme

Step 12

12 Reduce the heat to medium-low and cook, stirring frequently, until the onion is very soft and starting to brown, 15 minutes

Step 13

13 Pour in the wine, and stir in the sugar until it has dissolved

Step 14

14 Cook for another 2 to 3 minutes

Step 15

15 Transfer the mixture to a large bowl

Step 16

16 Combine the pecans and chestnuts in a food processor; pulse until reduced to small pieces

Step 17

17 Transfer to the bowl with the onion mixture, along with the bread crumbs, toasted sesame oil and salt

Step 18

18 Cut the mushrooms in half, and reserve all but one of the halves to form the center of your Wellington

Step 19

19 Cut the remaining half into small chunks and add those to the bowl for the filling

Step 20

20 Use your hands to thoroughly mix the filling

Step 21

21 Taste, and add toasted sesame oil and/or salt as needed

Step 22

22 When ready to assemble, preheat the oven to 350 degrees

Step 23

23 Lightly flour a large piece of parchment paper

Step 24

24 Roll out the puff pastry dough on it to form a 10-by-14-inch rectangle that's about 1/8 inch thick

Step 25

25 Trim the edges of the dough to make it tidy; reserve the excess for decorating the top of the Wellington

Step 26

26 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

Step 27

27 Arrange the portobello halves evenly over the mixture down the middle of the dough, then cover with the remaining filling

Step 28

28 (You may have more filling and/or mushrooms than you need; save them for another use

Step 29

29 )

Step 30

30 Brush the borders of the dough with a little cream

Step 31

31 Fold over the ends and sides to wrap the dough around the filling

Step 32

32 (Use the parchment paper to help if needed

Step 33

33 ) The dough should overlap in the middle; stretch it gently if needed

Step 34

34 If there is a gap, use your excess dough to cover it, using cream to hold it in place

Step 35

35 Use the parchment paper to lift the Wellington onto the prepared baking sheet, turning it over so the seam is on the bottom

Step 36

36 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

Step 37

37 Bake the Wellington until puffed, golden brown and heated through, 60 to 75 minutes

Step 38

38 Let cool for at least 10 minutes

Step 39

39 Cut into thick slices and serve warm or at room temperature