Grease a 6 hole ‘Texas’ muffin tin (see FAQ’s) and set aside. Place the flour, butter, sugar and salt in the bowl of a food processor with the blade attachment fitted. Process on high until the mixture resembles fine bread crumbs, then pour in the beaten egg yolk and process until the dough clumps together, approximately 1 minute. If the dough is not coming together add 1 Tbsp of ice water.

Turn the dough out onto a lightly floured surface, knead a few times until the dough is smooth, then shape into a ball. Dust again with flour and roll out to the thickness of a fat coin. Use a saucer or similar as a guide to cut out 4 rounds of pastry and press them into the prepared tin. Stack up the remaining dough, roll it out again and cut out the remaining two pastry cases, dusting with flour as necessary to stop the dough from sticking. Transfer the muffin tin to the fridge while you prepare the filling.

To make the filling, heat the butter and oil in a large, heavy-based saucepan. Add the chicken to the pan and cook, stirring occasionally until it is no longer pink, around 3-4 minutes. Remove the chicken from the pan with a slotted spoon, and set aside in a bowl. Add the carrot, celery and spring onions to the pan season with a little salt and pepper then cook gently for 5 minutes until the carrot has softened. Add the mushrooms, bacon and thyme to the pan and cook for a further 3 minutes.

Pour the white wine into the pan, and use a wooden spoon to scrape off all the browned on flavour on the bottom of the pan. Stir the cornflour into the milk until smooth, then pour into the pan, stirring until well combined. Sprinkle over the chicken stock powder, then bring to the boil. Turn the heat down to low, add the chicken and juices to the pan, and simmer for 3 minutes, stirring. Remove from the heat and set aside to cool for 15 minutes.

Heat the oven to 200°C / 400°F / Gas 6 and place a baking tray on the middle shelf of the oven. Cut the puff pastry into 12cm squares and beat the egg yolk in a small bowl with 1 Tbsp cold water.

When the filling has cooled, remove the pastry cases from the fridge, divide the filling evenly between the cases, then top each with a square of puff pastry, pinching and crimping the edges to seal. Brush with the beaten egg, sprinkle over the poppy seeds if using, then cut a small slit in the middle of each pie to allow steam to escape. Bake in the preheated oven for 40 minutes, until puffed and golden brown.

Allow to cool in the tin for 10 minutes before lifting out. Twist each gently to loosen, then tip the tin and use a thin knife to help you. You may find it easier to place a cooling rack on the top, then invert the pies instead. Serve with cooked vegetables or salad.