1. When you’re ready for the folding stage, roll the dough out on a well-floured surface, using a floured rolling pin, to a rectangle of about 20 x 40cm. Have a bowl with sugar ready by your side and sprinkle the dough with about a tablespoon at a time at each folding.
2. With the short side facing you, fold the dough in thirds like a letter, bringing the top third of the dough down, then folding the bottom third up. If it sticks, throw some more flour at it and use a dough scraper to detach it. Rotate the dough 90 degrees. Repeat the rolling, sprinkling with sugar and folding process, then rotate the dough once more and roll and fold again. As you work, dust the work surface, your hands and the rolling pin with flour as necessary. Wrap the dough in plastic wrap and refrigerate for at least 1 hour.
3. Repeat the entire three-times-rolling, sugar sprinkling and folding process again – the dough should start to become smoother. If it’s still sticky, chill it for a bit longer and fold once more. Wrap the dough and refrigerate for at least 3 hours, or overnight.
4. When you’re ready to make the pastries, butter each hole in a 12-hole large muffin tin.
5. Roll the chilled dough out to a rectangle 30 x 20cm (12 x 9 inch). Trim the edges and spread most of the soft butter over the dough; sprinkle liberally with sugar. Now cut the dough into twelve 8 x 8cm (3in) squares using a sharp knife or a pastry cutter.
6. Sprinkle more sugar over the squares and fold all the corners of each square into the middle. Brush each pastry with more butter over the folds and place them in the muffin tin. Wrap the tin in cling film or a plastic bag and chill for at least 3 hours, or overnight.
7. Preheat the oven to 200C/400F/gas 6. Unwrap the tin and sprinkle any remaining sugar over each pastry. Bake for 30-40 minutes until they are deep golden brown and caramelised.
8. Remove the tin from the oven and cool on a rack a little, then scoop the pastries out with a spoon. Serve them warm or cold; keep the rest in an airtight box for a couple of days or freeze the surplus.