Place ingredients (a) in a mixing bowl and process with a dough hook at a slow speed for two minutes until well-combined.
Turn the machine on to medium speed and knead for two minutes until dough is smooth and elastic. Remove the dough hook. Cover the mixing bowl tightly with cling film and leave aside to prove for one hour until dough doubles in bulk.
Punch down the dough, then add ingredients (b) and milk. Attach the dough hook to the machine and knead on slow speed for two minutes, then on medium speed for two more minutes.
Lastly, add butter and knead on slow speed for one minute, followed by medium speed for six to eight minutes until dough is smooth and firm. Place dough on a lightly-floured surface. Cover with a damp tea towel and leave aside for 15 minutes.
Knock down dough, cut into equal pieces of 150g each and roll into balls with lightly-floured hands. Cover with tea towel and put aside for 10 minutes.
Roll each piece flat, then roll up swiss roll-style and turn into a tight u-shape. Place three pieces side by side on a lightly greased loaf tin.
Cover tightly with a piece of cling film and set aside to rise about three quarters up the sides of the tin, or about 30 to 45 minutes, for the final proving.
Glaze with beaten egg or milk and bake in a preheated oven at 180 ºC for 25 to 30 minutes, or till golden brown.