Add the levain, milk to a mixing bowl and mix until it looks like a milky liquid.
Next add the flour and mix until a rough looking dough is formed.
Rest the dough for 2 hours. This step is called autolysis. This process helps to build the dough and strengthen it.
After 2 hours, add the salt and 1 Tbsp. butter and knead until fully integrated. Follow until all the butter is added 1 T at a time. About 10-15 mins.
Cover with a clean cloth and rest for 1 hour and do a coil fold. Repeat this 3 more times at 45 mins interval. Total 4 coil folds.
Cover with a lid and place in the fridge. Bulk ferment for 15 hours.
Next day, take out the dough from the fridge. Let it rest for 15 mins. Divide the dough into 3 equal parts.
Gently roll them out into a rectangle about 5X20 inches using a rolling pin.
Fold them in starting with 1 end into a roll. Repeat with all 3 rolls.
Cover the rolls and rest for 30 mins.
Lastly roll out each one with a rolling pin again.
Fold them in starting with 1 end into a roll. Repeat with all 3 and place them in a bread pan side by side.
Cover and rest for 6-7 hours. The dough will rise above the bread pan by the end of 6 hours.
When ready to bake, pre-heat the oven for 390 deg. Place in the oven and cook for 25 mins. Reduce the heat to 350 and bake for another 10 mins.
Once out brush with some butter, slice them and enjoy!