In a large bowl, combine the warm water, active starter, milk, honey, and 585g of the flour. Mix by hand or with a dough hook. The sponge will be soupier than a dough ball at this point. Cover and let rest 20 minutes.
Mix in the salt, olive oil, and the rest of the flour. The dough should be a loose but not too sticky ball with everything incorporated and no lumps. Cover and let rest on the counter at least 8 hours (overnight).
By morning the dough should have at least doubled. Grease 2 to 3 loaf pans (4×8 and/or 5×9). Gently scrape the dough out onto a floured surface.
Stretch the dough into a rectangle and divide into 2 or 3 equal sections (depending on pan size). Stretch each into an even rectangle, then roll it up cinnamon-roll style. Turn the loaf 90 degrees, tuck each end under, and build some tension before placing it in the greased pan.
Cover the loaves with a tea towel and let rise 2 more hours. Preheat the oven to 400F about 20 minutes before baking.
Place the loaves on the middle rack, lower the temperature to 350F, and bake 45 to 55 minutes, until the internal temperature is above 200F.
Coat the tops with butter, let rest in the pans 5 minutes, then transfer to a wire rack. Store in an airtight container up to a week, or wrap tightly and freeze.
