250g chestnut mushrooms, very finely chopped (or blitzed in the food processor)
5 sprigs of thyme, leaves picked and chopped
80g walnuts, very finely chopped
1 tbsp sherry vinegar
A good grating of fresh nutmeg
200g full fat cream cheese
1 lemon, zest only
Freshly ground black pepper
Preheat the oven to 180*C. Line a baking tray with parchment.
Remove any outer leaves and the tough bottom stalk from the cauliflower, while keeping it whole. Rub with the olive oil and some salt and pepper and roast for 30 minutes until almost tender and golden brown. When cooked, remove from the oven and allow to cool completely.
Soak the porcini mushrooms in enough boiling water to cover them. Set aside for 30 minutes while you make the rest of your filling. Sweat the shallots in the olive oil in a frying pan until very soft and beginning to get some colour, at least 10 minutes. Add the garlic and cook for another minute. Turn up the heat and add the mushrooms and fry off until they are golden brown - this takes longer than you think, around 12-15 minutes. By now, you should be able to drain off the porcini mushrooms (reserving the liquid for later), finely chop them and add to the pan. Continue to cook until you can see that no liquid remains in the pan and the mixture is dry. Add the thyme & walnuts and cook for a further few minutes, then add the sherry vinegar, cook until you can see no liquid and remove from the heat. Mix with the cream cheese, nutmeg and lemon zest and season to taste - it should be quite highly seasoned as cauliflower can be quite bland. Set aside to cool.
Roll out one of the puff pastry sheets and place the cooled cauliflower on top. Spread the mushroom mixture all over the cauliflower, but do not put any on the base. Brush a ring around the base of the cauliflower with egg wash to help the two sheets join, then cover the top with another sheet of puff pastry, and smooth down from the top making sure you’ve left no big air pockets and have no creases. Leave a 2cm border at the base, but make sure the cauliflower is tucked in tightly. Trim off the excess from both sheets of pastry, and then fold up the scraps together and re-roll to a 3mm thick sheet
Using a sharp knife make a series of 2-3cm slits in staggered rows, 1cm apart. Gently pull the pastry so that the slits open up and a lattice pattern reveals itself. Egg wash the smooth pastry that already covers the cauliflower, then drape the lattice pastry over. Seal at the border with a fork, remove any excess, then egg wash the lattice.
Bake for 15-20 minutes until golden brown all over.
While you wait, mix the two tablespoons of instant gravy powder with 100 millilitres boiling water and enough of the reserved mushroom soaking liquid to make an intensely mushroomy cheat gravy! Slice and serve.