For the pastry: Cube the baking block and place in the freezer for 10 minutes. Then put the flour and salt into a large bowl, add the chilled baking block and using a blunt knife roughly mix the baking block into the flour. You want to maintain lumps of the baking block, 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. Wrap the dough in clingfilm and chill in the fridge for 15minutes. Then repeat the rolling/folding process, turn the dough 90 degrees so the open ends are facing you and repeat the rolling and folding process again. Place in the fridge for 30 minutes, then repeat the rolling and folding process twice more, before chilling again for atleast 1hour or until needed.
For the filling: Meanwhile, chop the butternut squash into small cubes and place into a large baking tray. Scatter over 1tbsp of the oil and the cinnamon, mix to thoroughly combine and then bake in the oven for 45mins at 200C/Fan 180C.
Finely slice the onions. Place the remaining tbsp of oil into a medium frying pan, and place over a medium-low heat with the onions. Cook, stirring every now and then, until the onions begin to caramelise. Take off the heat and set aside.
Once the butternut squash is cooked and very soft, place in a large bowl and mash thoroughly. Add the caramelised onions, lemon zest +juice, pine nuts, olives and breadcrumbs. Finely chop the sage and parsley and add to the bowl. Season to taste, and mix to combine all ingredients thoroughly. Set aside.
Preheat the oven to 200C/180C Fan and place baking paper over a large baking tray.
To assemble: Roll the chilled pastry out into a large square – approx. 40cm. Then divide into three rectangles, with the short ends facing you. Spoon the filling down the middle of each pastry rectangle, then using a pastry brush, brush oil on either side of the filling. Then fold each side of the pastry over to create a seal. Then turn each roll over so the seal is underneath. Cut the rolls into 4, so you end up with 12 rolls. Poke two holes into the top of each roll, then brush with oil. Place on the baking tray, and bake for 35 minutes. Grill for a few minutes to get a golden colour if desired.
Best eaten on day of baking. Rolls can be kept in an air-tight container for 2-3 days.