For the pastry: Put the flour and salt into a large bowl. Add the cubed butter and using a blunt knife roughly mix the butter into the flour. You want to maintain lumps of butter, so don’t mix too hard. Pour in half of the water and stir to combine, then pour in the remaining water until the mixture just comes together (you may not need all the water).
Tip the mixture out onto a floured work surface and roll into a long rectangle with the short edge facing you. You want it to be around 15cmx45cm. Then fold the top third of the dough down over the middle third, and fold the bottom third up over the two-thirds, as if you are folding a letter. Turn the dough 90 degrees so the open ends are facing you and repeat the rolling and folding process. Place in the fridge for 30 minutes, then repeat the rolling and folding process twice more, before chilling again for 1hour.
Preheat the oven to 200C/180C Fan and place baking paper over a large baking tray.
For the filling: Firstly dice the red onions and place in a large saucepan over a medium-high heat with a little oil and cook until softened. Then set aside to cool. In a large bowl add the sausagemeat, egg, breadcrumbs, mixed herbs, garlic granules and combine thoroughly – it may be easier to use your hands. Peel, core and finely chop the apples and add to the mix until combined. Then season well.
To assemble: Roll the chilled pastry out into a large rectangle – approx. 35x50cm. Then divide into three rows, and divide these into 4 squares. You will end up with 12 squares of pastry. Divide the sausagemeat mixture between these squares, placing them in a sausage shape in the middle. Leaving a large gap to the right and left, and a smaller gap at the top and bottom.
Using a pastry brush, brush the beaten egg on all the exposed pastry. Then for each pastry square, fold the right side over the sausage filling and then the left. Pressing down to seal. Then roll each over, so the seam is now at the bottom. Finally, using scissors cut small triangles out of each end of the sausage rolls to create the cracker shape - it may be easier to pick each roll up to do this.
Place the rolls onto the baking tray and brush the remaining beaten egg over each sausage roll. Bake for 35mins until golden brown. Leave to cool a little, then enjoy.
Sausage rolls can be kept in an air-tight container in the fridge for up to 4 days.