Firstly, preheat the oven to 200C/180C Fan/Gas Mark 6 and line a large baking tray with baking paper.
Mix together the brown sugar and spices in a small bowl until evenly combined. Then lay out the sheet of puff pastry onto a lightly floured worksurface. Then sprinkle the sugar spice mix evenly on top. Then using the palm of your hand press down slightly, to press the sugar spice mix into the pastry. Then fold the pastry in half width-ways, like closing a book.
Cut the pastry 'book' into 8 strips horizontally, ensuring they are all the same width. Take one strip and press down slightly along the length, to help the secure the pastry so the filling doesn't spill out. Then pick up the strip, holding each end in your hands and flip it over so it's facing 'down', and the middle of the strip is resting on the worksurface. Then bend just the ends back and across each other. Let go of the ends, and press down slightly on the whole pastry to secure it. Repeat the twisting process for all the pastry strips and then carefully place them onto a large baking tray, leaving space around each to grow.
Beat the egg briefly in a small bowl, and then using a pastry brush, glaze over each pastry. Finally, sprinkle each with Demerara sugar before baking in the oven for 12-15 minutes until golden brown and bubbling. Enjoy warm.