First thing in the morning, feed your starter in the ratio of 1 part starter: 1 part flour: 1 part water and leave it for 4-6 hours to at least double in volume. Alternatively, feed your starter the night before in the ratio of 1 part starter : 2 parts flour : 2 parts water and leave it to grow overnight.
Once your starter has doubled in volume, heat the milk and butter in a small saucepan until the butter melts, then leave to cool down to just warmer than room temperature.
Mix flour, salt, milk mixture, starter, and honey in a bowl of our standing mixer. Fit the mixer with a dough hook attachment. Start running the stand mixer on low speed until the ingredients are incorporated, then increase the speed and knead for 6-7 minutes.
Tip the dough onto a clean surface and using a dough scraper tuck the sides under in swift motion to form a tight ball of dough.
Place the dough in a lightly greased bowl, cover and leave in a warm spot for 30 minutes. After 30 minutes, lift one side of the dough and fold it into the centre. Repeat with the other three sides. Then flip the dough over. Alternatively, perform coil folds. Cover and leave again for 30 minutes.
After 30 minutes, fold and stretch again using your preferred method. Do so two more times (4 times in total). Cover and leave in a warm spot to prove for 2 hours. The dough should have considerably risen during this time.
Cover the dough very well and pop it in the fridge to continue slow proving overnight.
Take the dough out of the fridge in the morning and leave it at room temperature whilst you lightly grease a large loaf tin with some oil.
Turn the dough out onto a lightly floured surface. Trying to keep the air in the dough as much as possible, stretch the dough into a rectangle, the length of your loaf tin. Then roll the dough to form a tight log.
Place the dough log into the tin, cover with a damp tea towel or oiled cling film and leave in a warm spot to rise until the dough is doubled in size, about 2 hours.
Preheat the oven to 180°C Fan. Uncover the dough. Using a very sharp knife, a razor or a bread scorer, make a couple of slashes across the dough. Brush the top of the loaf with beaten egg.
Bake 30-35 minutes until golden brown. If you have a kitchen thermometer, check that the internal temperature is 88-93° C. Leave the loaf to cool down in the tin for 10 minutes, then transfer it onto a cooling rack to cool completely before slicing.
