To a stand mixer add 1 cup of starter with warm milk and water. Add sugar and mix everything together. You can mix everything in a bowl by hand, without using mixer.
Add 4 cups of flour to the mixture and mix everything together.
Melt butter and add to the dough with salt and 2 last cups of flour. Mix everything well
Get dough out of mixing bowl and kneed for 5 minutes. Leave it for 30 minutes covered with towel.
Kneed dough again for 5 min and leave it to rise for 6 hours.
After 6 hours divide dough for 2 equal pieces.
Roll dough and make rectangle shape.
Add shaped dough to parchment lined loaf pans
Cover with wet towel and let it second rise for 3-4 hours, until it is doubled.
Bake at 385 for 50 minutes, or until golden on top.
Get bread out of pans and allow to cool it completely before cutting. You can put some butter on top of the cooling bread if you want it to be soft.