Porcini, tarragon, crème fraîche help make this Pithivier pie perfection

I’m on a puff pastry roll at the moment. So to speak. No sooner had I hymned the praises of the vol au vent than I was grappling with another traditional French pie. Thanks to the arrival of a remarkable debut cookbook called simply Butter (Headline, £26). Spread the word (sic). Its author Olivia  Potts, The Spectator magazine’s ‘Vintage Chef’ and ‘Table Talk’ podcaster, is a bright new star in the cookery writer firmament. Already I’ve followed her book’ advice to make my own cultured butter, recycling the buttermilk created into a soda bread loaf; funkier till, twice I’ve filled hasselback potatoes with her signature kimchi and blue cheese butter.

With a glut of mushrooms on my hand what better next than her fungi-filled pithivier recipe? A big welcome to Wild Mushroom, Tarragon and Crème Fraîche Pithivier, which ticks so many of my boxes.

Originating in the eponymous town south of Paris that is twinned with Ashby-de-la-Zouch, the pithivier can accommodate savoury or sweet fillings under its distinctive fluted pastry dome. My own rather tasty effort (main picture) didn’t quite attain the classic round shape (see Olivia’s version below) thanks to my clumsy cutting of bought-in puff pastry. Olivia, though, is no stickler over the necessity to make your own. 

Indeed she offers a cautionary tale in the book. Volunteering to work in a Crisis at Christmas kitchen, she arrived to realise that she was in charge and no ready-made puff was in the walk-in fridge for the pies she had promised – just the separate ingredients. For a former criminal barrister this was judgement day! She rose to the occasion, making 6kg of pastry by hand, but admits: “I just about had RSI by the end but have rarely been prouder.”

If you must follow her lead, albeit on a smaller scale, Butter offers various versions, from decidedly flaky ‘rough’ to the smoothly laminated classic recipe and, finally ‘inverse’, which swaps the method. Rather than the base dough being wrapped around  butter block, and then folded to distribute even layers of the butter, the butter is wrapped around a dough block and then folded similarly.

As I said, I bought in mine, pure butter, of course, but with the proviso from an organic supplier, dorset pastry, which has no truck with the controversial and possibly harmful commercial additive, L-Cysteine (E920) (a dough relaxant derived from animal hair and feathers), which legally need not be disclosed on a pastry or bread label. It’s commonly used in the Chorleywood bread-making process. Think white pap. Say no more.

For something genuinely worth eating let’s visit Olivia’s recipe for Wild Mushroom, Tarragon and Crème Fraîche Pithivier (serves four) …

“Pithiviers are round puff pastry pies, with filling sandwiched between them. I think the word ‘pie’ in any context immediately summons up the idea of something heavy, something sturdy.While sturdiness is no bad thing, that is not what we’re dealing with here: pithiviers are the spiderwebs of pies, light, fragile, a feat of architecture. Pithiviers tend to be intricately decorated with knife marks, radiating or zig-zagging out from the centre, like fractals.

“As a pie, you can fill it with anything that takes your fancy… but for the best results, I use a filling that you can chill firm, so that when you shape the pastry round it and bake it, it will retain its beautiful domed shape. I use inverse puff pastry here, because the pithivier is such a handsome, proud dish that it makes the most of my hard laminating work, but you can use any puff you have – shop-bought is, of course, completely fine.”

Ingredients

20g dried porcini mushrooms; 150g oyster mushrooms; 250g chestnut mushrooms; 15g butter; 1tbsp cider or white wine vinegar; 3tbsp crème fraiche; 1 tbsp shredded fresh tarragon; ½tsp fine salt; freshly ground black pepper; 300g puff or inverse puff pastry; 1 egg yolk, beaten, to glaze.

Method

1. First, cover the dried porcini mushrooms in boiling water, and leave to soak while you cook the other mushrooms.

2. While the porcini are soaking, halve the oyster mushrooms and slice them, and slice the chestnut mushrooms. Heat a heavy-based frying pan over a medium-high heat and melt the butter in it. Sauté the oyster mushrooms until golden-brown, add the vinegar, let it cook off, then set the mushrooms to one side. Cook the chestnut mushrooms in the same pan until they have given up their water and begun to sizzle.

3. Drain and roughly chop the rehydrated porcini mushrooms. Combine the porcini, oyster, and chestnut mushrooms, along with the crème fraîche and the tarragon, and season generously with the salt and some pepper. Line a bowl approximately 15cm across with clingfilm, spoon the creamy mushroom mixture into it, pack it down into an even layer (don’t worry, it won’t fill the bowl) and freeze for an hour until firm.

4. Meanwhile, roll out the puff pastry to the thickness of a pound coin. Later, you’re going to need to cut one 20cm and one 23cm disc from the pastry, so check that your rolled pastry is big enough to accommodate this. Divide the pastry in half, then transfer the two sheets of pastry on to a chopping board or tray with a sheet of baking paper between them. Refrigerate for at least 30 minutes.

5. Cut out two discs, one 23cm, one 20cm, from the chilled pastry. Place the smaller disc on a baking paper-lined baking tray.Turn the chilled mushroom mixture out on to the centre of the pastry, removing the clingfilm from it, and dab a border of water around the edge of the pastry. Lay the second, larger disc on top. Smooth the top layer of pastry down over the mixture, to reduce air bubbles, and press the edges down with the tines of a fork to seal. Paint all over with egg yolk, and refrigerate for 20 minutes.

6. Preheat the oven to 200°C. Paint the pastry with another coat of egg yolk and then, using the back of a small knife, make swooping marks from the centre of the pastry down towards the edge. Prick a hole in the centre, to act as a vent. Bake for 15 minutes, then drop the temperature to 170°C and bake for another 45 minutes until puffed and golden. Serve hot.