Autolyse flour and water for an hour (You can skip this step but this shortens the kneading time later on).
Add levain and salt and mix well.
Add (softened) butter, knead well until you get a smooth homogenous dough.
Leave the dough to proof until double, giving it a fold every 30 minutes for the first 2 hours.
Cold retard overnight (or you can do a same day bake too).
Tip the dough out onto a well-oiled tray and let it proof.
Preheat oven at 250C for at least 30min.
Gently stretch the dough outwards towards the rim of the pan and dimple it. Add your favorite toppings.
Bake the focaccia at 230C for 20 to 25 minutes.
