380g water (~20ºc)
7g instant yeast
630g strong white bread flour
25g castor sugar
30g milk powder
Remove the butter from the fridge and flatten it between 2 pieces of baking parchment.
Combine all of the ingredients except the butter in the bowl of a stand mixer. Mix on slow speed for 5 minutes.
Increase the mixer speed to medium, and add the butter piece by piece. Once all the butter is completely incorporated, mix for an additional 5 minutes. The dough should be soft and elastic with a smooth skin. If not, continue to knead a few more minutes.
Cover the dough and let it prove for 90 minutes, folding once after 45 minutes.
Lubricate a 33cm Pullman pan with vegetable oil
Carefully turn the dough onto a lightly floured surface. Gently deflate the dough and form into a rough square shape, and divide roughly in half.
Shape each piece into a sausage about 50cm long. Rest for 5 minutes under a tea towel. Twist the ropes together and transfer to the pullman pan.
Put the lid on the pan and close loosely for second prove. The dough will take about an hour to reach the top of the pan in a warm kitchen. When the dough is very close to the top of the pan, close the lid completely and put into the preheated oven.
Bake at 230ºc for 10 minutes. Lower the temperature to 175ºc and bake for another 25 minutes. Remove the lid from the pan and bake for another 10 minutes to brown the top of the loaf.
Turn loaf out onto a wire rack. If the sides and bottom are still pale and flimsy, return the loaf to the oven for 5 minutes, inverted on a baking tray.
Leave to cool completely.