You need to start by making the filling. So, first of all, cut the chicken into ½ inch (1 cm) pieces, then place them in a bowl, add the mace and season with salt and pepper.
Now, in a separate bowl, combine the sausagemeat with the spring onions, the chopped thyme, sage, parsley, lemon juice and zest. Add the cream and mix everything together well.
Pre-heat the oven to gas mark 4, 350°F (180°C).
Now for the pastry, put the milk and 2 fl oz (55 ml) water into a small saucepan and add the vegetable fat, cut up into small pieces. Place the pan over a gentle heat and simmer until the fat has dissolved.
Sift the flour, mustard, mixed spice, sea salt and nutmeg into a large mixing bowl, and mix in 1 of the egg yolks so that it is evenly distributed. When the fat has completely melted in the liquid, turn up the heat to bring it just up to the boil, and pour it on to the dry ingredients then, using a wooden spoon, mix it all together.
Then turn the dough out on to a lightly floured work surface and bring it together with your hands to make a ball. You have to work quickly now, as it's important that the pies go into the tin whilst this dough is still warm.
Take two-thirds of the dough and cut this up into 6 equal parts. Roll each of these into a ball and put 1 into each of the holes in the tin. Using your thumb, quickly press each ball flat on to the base and then up to the top edge. Press the pastry over the rim of the top edge; it should overlap by at least ¼ inch (5 mm).
Using a teaspoon, divide half of the sausagemeat among the 6 pies. Then follow this with the chicken and then the rest of the sausagemeat, pressing the filling in firmly as you go.
Then roll out the remaining pastry and cut out six 3¼ inch (8 cm) rounds; the pastry will be quite thin, so you may need to sprinkle the work surface with a little extra flour.
Next, using a fork, lightly beat the remaining 2 egg yolks together in a small bowl. Then, using a pastry brush, paint some of the egg yolk round the upper edge of the pies and gently press on the lids.
Using a small fork, press the rim of each lid against the top of the pie case, make a hole in the top of each pie and glaze with the rest of the yolk. Finally, push a small sprig of thyme into the top of each pie. Now place the muffin tin on the baking sheet and bake the pies for 30 minutes on the middle shelf.
After this time, using oven gloves or a thick cloth, carefully remove the hot pies from the tin and place them directly on to the hot baking sheet, a small round-ended knife is useful for getting the pies out of the tin.
Glaze the sides of the pies with the remaining egg yolk and return them to the oven for a further 20 minutes or until the sides and base of the pies are crispy, then leave them to cool on a wire rack.
When cold, store in an airtight container in the fridge; they'll keep like this for a couple of days, but bring them to room temperature before eating.