Mix the ingredients for plain dough and knead until smooth. Wrap and chill for 30 minutes.

Mix all the ingredients for olive oil dough, kneading until smooth. Wrap and chill for 30 minutes.

Lightly dust a bench with flour and roll the olive oil pastry out to about 1cm thick. Roll the plain dough out until large enough to cover the olive oil dough. Place the olive oil dough on top of the plain one and fold over the edges until they meet in the middle. Roll the dough out to 1cm thick, fold into thirds, repeat the rolling and folding procedure and chill for another 30 minutes. Do this twice more, chilling between each turn.

Finally roll out the dough thinly and cut out circles large enough to cover six 6cm pie dishes, with an overhang.

Heat the oven to 190°C.

Heat a large frying pan over a moderate heat and add the olive oil. Add the shallots to the oil and cook for 10 minutes, until soft and lightly coloured.

Sort the mushrooms, washing and peeling them, then halve, quarter or slice as needed. Add the mushrooms to the pan and cook for a minute without stirring, adding more oil if necessary. Stir the mushrooms and add the lemon zest. Continue cooking for several minutes until the mushrooms have softened.

Pour in the vegetable stock, increase the heat, season with salt and pepper and simmer for about 8 minutes, until the stock has reduced and the mushrooms are relatively little left. Stir the tarragon leaves into the sauce.

Divide the mushroom mixture equally between the pie dishes.

Cut the havarti cheese into small pieces and sprinkle over the top of the mushrooms.

Brush the pastry rounds with water and place over the top of the pie dishes, water-side down. Press carefully around the edges to form a seal. Brush the top of the pastry with the beaten egg and sprinkle with a little coarse sea salt.

Place the pie dishes onto a flat tray and bake in the oven for about 20 minutes, until golden.