Step 1

First make the filling. Heat the oil and butter in large frying pan and add the onion and celery. Cook until the onion is starting to caramelise, then add the grated vegetables. Continue to cook, stirring regularly, until they have reduced down considerably. Season with salt and pepper and stir in the garlic and herbs. Continue to cook for another 2–3 minutes then stir in the lemon zest and spices. Set aside to cool. When cool, stir in all the remaining filling ingredients and set aside.

Step 2

For the outer filling, heat the oil and butter in a frying pan and add the shallots. Gently fry until translucent, then add the mushrooms and garlic. Cook until the mushrooms have reduced in volume and any liquid has evaporated – the texture should almost be that of a mushroom pate. Wilt down the spinach in a little water, then drain and finely chop. Squeeze as much water out as you can, then stir through the mushrooms and lemon juice, to taste. Set aside to cool completely.

Step 3

To assemble, put the prunes in a small saucepan and cover with the sherry or Marsala. Bring to the boil then remove from the heat and leave the prunes to absorb the sherry.

Step 4

Preheat the oven to 200C/180C Fan/Gas Line a baking sheet or tray with baking paper.

Step 5

To assemble the Wellington, flour a large piece of baking paper and roll the puff pastry out to around 30cm–40cm/12–16in. Spread a quarter of the cold mushroom mixture lengthways down the middle of the puff pastry, leaving a border on both short sides.

Step 6

Pile half the filling mixture on top, then put a line of the prunes along the centre. Add the rest of the filling, making sure it seamlessly joins together, then spread the rest of the mushroom mixture on the top and sides of the filling.

Step 7

Brush the edges of the pastry with egg wash, then bring up the sides to cover the filling and slightly overlap. Seal the ends, trimming a little if you want to then carefully roll onto the lined baking tray so the join is on the bottom.

Step 8

Cut a few slashes in the top to help steam escape and brush with more egg wash. Use any offcuts of pastry to decorate, if you wish. Bake for around 35 minutes, or until the Wellington is rich golden-brown and piping hot. Leave to stand for 10 minutes before cutting into it.

Step 9

Meanwhile to make the gravy, heat the olive oil and butter in a saucepan. Add the shallot and fry on a medium-high heat until it has softened and caramelised. Add the mushrooms and cook until they have reduced down and are dry.

Step 10

Stir in the garlic and thyme, and season with salt and pepper. Stir in the flour and cook for a couple of minutes, stirring constantly, then turn up the heat and add the wine. Bring to the boil, stirring constantly, then add the mushroom ketchup and stock a little at a time until it has all been added and you have a fairly thin gravy. Taste and add more seasoning if needed. Strain through a sieve if you prefer it smooth or serve as is.

Step 11

To make the cranberry sauce, put the cranberries, orange (or clementine) juice and zest, and sugar into a saucepan. Add a splash of water and cook over a gentle heat, stirring to dissolve the sugar.

Step 12

When most of the cranberries have burst and the sauce has thickened, taste and add a little more sugar if necessary. Stir in the sherry or port and simmer for another minute. Transfer to a serving bowl and allow to cool.

Step 13

When the wellington is ready, slice into pieces and serve with gravy and cranberry sauce.