Step 1

Start by blitzing/chopping the chestnut/baby bella mushrooms until they're roughly chopped. For the shiitake, simply de-stem (as the stems are often too fibrous to use) and thinly slice the caps. For the oyster mushrooms, tear these into thin strips

Step 2

Heat a wide non-stick pan over a high heat and caramelise all of the mushrooms in batches (no oil or salt needed). Do this in batches to prevent over crowding the pan which would cause the mushrooms to steam and turn soggy. Once they smell nutty and look caramelised, transfer them to a mixing bowl or tray and season lightly with a pinch of salt. You may need to add a touch of olive oil towards the end of cooking if you're finding the mushrooms sticking to the pan

Step 3

To make the mirepoix, start by blitzing the carrots, celery, and onion in a food processor until finely chopped. Alternatively, you could also do this by hand with a sharp knife

Step 4

Next, heat a pan with the olive oil over a low heat and sauté the mirepoix low and slow for around 10-15 minutes

Step 5

Once the moisture has been sweated out, it's time to season. Mix the miso paste and tomato paste with 4tbsp boiling water until it forms a smooth paste

Step 6

Then, add the miso tomato mixture to the mirepoix along with the garlic and fresh herbs

Step 7

Cook everything together on a low heat for a further 2-3 minutes. Then add the mirepoix mixture to the mushrooms and mix well to combine. Allow to cool slightly (~10 minutes)

Step 8

Finally, add in the wholegrain mustard. And then to bind, add in the instant mash and cornflour (cornflour for UK readers and corn starch for US readers). Mix well to combine, then set aside to cool completely. As the miso and instant mash contain salt, I wait until this point to check for seasoning and adjust if needed

Step 9

For ease, assemble the wellington on a large sheet of baking paper/or the sheet it comes rolled in. This will make it easier to move around

Step 10

Start by placing the cooled mushroom filling in the centre (lengthways) of one puff pastry sheet. Then shape neatly and tightly into a half log with 2 inches of pastry either side and just over an inch front and back. The wellington will flatten slightly during baking so aim for more height here

Step 11

Then, place the second sheet of pastry directly over the mushroom filling and seal tightly all around. If there are any trapped air bubbles, these will puff up during the bake

Step 12

Move the baking paper and wellington on to a chopping board/baking sheet and wrap the wellington tightly in 2 layers of clingwrap and place into the fridge to chill for at least 3 hours, or up to 2 days

Step 13

Preheat the oven to 190'C (fan)/210'C conventional - 375'F/410'F

Step 14

Transfer the baking paper and wellington on to a baking sheet (if not on one already). Trim off the excess pastry with a sharp knife and a clean cut, leaving around 2cm of pastry all around. For the corners, I prefer to use a round pizza cutter

Step 15

Crimp the edges of the pastry all around with a fork. And then make light scores on the surface of the pastry with a sharp knife. This can be in any pattern you desire

Step 16

Also, make 3 small horizontal slits in the top of the pastry for venting. Then brush the wellington all over with an egg wash or any alternative of choice (listed in the notes below)

Step 17

Place the wellington into the pre-heated oven and bake for 55 minutes or until golden brown and puffed up. Optionally, re-apply another layer of egg wash in the last 15 minutes of the bake for an extra glossy sheen (highly recommend!)

Step 18

Allow the wellington to cool for 15-20 minutes before cutting into, this will allow the mushroom filling to firm up. Don't worry, it will still be very warm!

Step 19

Slice with a sharp serrated knife and serve immediately