Place all the ingredients aside from the tourage butter in a large bowl, and mix until it forms a dough. Transfer to a clean work surface and knead until smooth and elastic; around 15 minutes by hand (if you're using a stand-mixer fitted with the hook attachment, check the dough after 10 minutes as gluten will develop considerably faster). Wrap in clingfilm and chill in the freezer for 30 to 45 minutes, until hard but not frozen; then transfer to the fridge overnight.
Make the syrup: bring the sugar and water to the boil, and allow to cool down at room temperature.
The next morning, cut the butter into 5mm thick slices and arrange on a large piece of baking paper. Roll to a 20x30cm rectangle.
Lightly flour your work surface and roll the dough into a 20x60cm rectangle. Place butter on lower half, then give the dough three tours simples, with at least 30 minutes of rest in between each.
Chill the dough for an hour, then roll into a 35cm wide rectangle, around 5mm thick and 60cm long.
Sprinkle the dough with the pearl sugar leaving a 5cm margin on one edge. Roll lightly using your rolling pin for the sugar to stick to the dough; then brush the "naked" edge with syrup.
Roll tightly, then wrap in clingfilm and chill in the freezer for 30 minutes, seam-side down.
Trim and slice into 4.5cm logs; or divide the dough in 12.
Place into two muffin tins, 6 rolls in each so they have plenty of space.
Cover loosely with clingfilm and proof for around 2 hours (at 24°C for me).
Bake at 190°C / fan 170°C for 30-35 minutes, or until golden-brown. Brush with the remaining syrup when still warm.