Mix starter, sugar, water, salt, and butter in the bowl of a stand mixer.
Add flour one cup at a time allowing it to incorporate before adding more.
Allow the mixer to knead the dough about 10 minutes.
Cover the dough with plastic wrap and set overnight. Allow it to rest 8-12 hours.
In the morning, cut the dough into six equal balls.
Stretch or roll the balls into rectangles. I stretched mine to about five inches.
Pull the bottom edge up toward the center and press down the seam.
Next, pull the top edge town and pinch the seam together.
Turn the dough over and lightly roll it back and forth to smooth the seam.
Place on a parchment lined baking sheet and cover with a damp towel. Allow to rest until doubled in size. This time frame will vary depending on the temperature of your kitchen.
Once doubled, score with a sharp knife or blade. Bake at 375° for 15-20 minutes