Heat the olive oil in a large saucepan set over a medium heat. Cook the onion and carrot for 5-6 minutes until softened. Increase the heat and add the chicken, sweet potatoes, mushrooms and soup. When the mixture comes to the boil, reduce the heat to a simmer and check the consistency. If it is too watery, add the cornflour mixed with 1 tbsp cold water, stirring all the time. Season, then cook for a few more minutes until the mixture thickens. Remove from the heat and set aside to cool completely. Heat the oven to 180 degrees celsius / fan 160 degrees celsius. Lightly grease a 6 cup muffin tin (each cup should have a diameter of 7.5cm and a depth of 3cm) with lard.

For the pastry, sift the flour, salt and nutmeg into a warmed bowl. Heat the lard with the milk and 75ml water in a small saucepan set over a low heat until the fat has melted, then bring to the boil. Make a well in the flour and drop in 1 egg yolk. Cover the yolk with a little flour, then quickly add the hot liquid mixture, stirring with a wooden spoon until mixed and cool enough to handle. Turn out the dough on a lightly floured board and knead it until it becomes pliable and soft. Shape the dough into a ball, put it on a warm plate and cover with an inverted bowl. Leave it in a warm place to rest for about 20 minutes.

Take two-thirds of the dough and cut this into 6 equal pieces. Keep the other third warm while making the pastry cases. Roll each of these into a ball and put 1 in each of the holes in the tin. Using your thumb, quickly press each ball onto the base and then up the sides to the edge. Press the pastry over the top edge, it should overlap by at least 5mm. Divide the filling into 6 equal parts and then spoon into the pie cases. Roll out the remaining pastry and cut out 6 rounds using an 8cm pastry cutter.

Using a fork, lightly beat the remaining egg yolk in a small bowl. Then, using a pastry brush, paint some egg yolk around the upper edges of the pastry and gently press on the lids. Use a small fork to press the rim of each lid against the top of each pie case, make a hole in the top of each pie, then glaze with the remaining yolk. Bake the pies for 40 minutes on the middle shelf of the oven. Leave them to cool on a wire rack. When cold, store pies in an airtight container in the refrigerator: they’ll keep like this for a couple of days, but bring them to room temperature before eating and garnish by sticking a little baby carrot into the hole of each pie.