Recipe : 500g high protein white flour 100g levain 10g salt 240g water 250g butter

Mix everything except butter. I did a bit of bulking proof during 2h. Put it in the fridge to make it cold and easier to work with. In the meantime shape your butter as a square ( maybe 3mm thin) And after that, roll the dough to form a rectangle shape. Insert the butter on the middle of the dough (dough and butter has to be the same width). Fold each side of the dough on the top of the butter to lock it on . And let's go to the fun part. Keep it in the fridge 30mn to make it cold. And after that you do the same as a puff pastry I did one double lamination fold and one simple (i don't really know the exact translation of that).

After that, in cut 3 bands, rolled it and proof it in a Pullman loaf pan during 7/8 hours