Method

1. For the shortcut puff pastry, mix the flour and salt together in a bowl. Rub in the chilled butter using your fingertips until the mixture resembles breadcrumbs. Gradually add enough water to form a dough (about 4-6 tablespoons of water).

2. Roll the dough out into a rectangle on a lightly floured work surface.

3. Coarsely grate the frozen butter over the bottom two-thirds of the dough. Fold down the top third and fold up the bottom third as if folding a letter.

4. Turn the folded dough 90 degrees on the work surface and roll out into a rectangle again.

5. Fold again in thirds, wrap the dough in cling film and set aside to rest in the fridge for 30 minutes. Repeat the rolling, folding and turning process a further two times, chilling in between each turn. In total you will have done four turns. Rest the pastry in the fridge while you make the filling.

6. Preheat the oven to 200C/400F/Gas 6.

7. For the filling, put the mushrooms in a food processor and season with salt and pepper. Pulse until the mushrooms are broken down to a rough paste. Add the thyme and give the mix a final pulse.

8. Put the mushroom mixture into a dry frying pan set over a medium-high heat and cook, stirring often, until all the moisture has evaporated from the mushrooms. Remove from the pan and leave to cool.

9. Meanwhile, using the same pan, heat the oil and butter over a medium-low heat. Add the onions and sugar and cook slowly until the onions are very soft and sweet. This will take at least 20 minutes. Once caramelised, stir in the sherry vinegar.

10. To assemble, roll out the pastry into a 60x45cm/24x18in rectangle, and cut into 12 squares.

11. Divide the mushroom mixture into 12 portions and spread a portion down the centre of each square of pastry, leaving a 2cm/1in gap at the top and bottom.

12. In a bowl, mix the sausage meat with the black pudding and mould into 12 sausage shapes. Place on top of the mushroom paste and then spread the caramelised onions on top of each sausage.

13. Make two small diagonal cuts from each corner of the pastry, to remove a small triangle. Then fold the top and bottom 'wings' over the ends of the sausage meat. Cut a 1cm/½in fringe all the way down the pastry on each side of the filling. Bring one strip over the filling from one side, then one from the other and so on, crossing the strips over to form a plaited effect. Tuck the ends of the pastry under the plait, trimming off any excess if necessary.

14. Repeat with the remaining squares of pastry until you have 12 mini sausage plaits. Place the plaits on a baking tray, brush with beaten egg and sprinkle with sesame seeds.

15. Bake for 20 minutes, until the pastry is golden-brown. Leave to cool for five minutes or so, then serve hot or cold.