Cut butter into pieces and set aside on a plate to come to room temperature.

Mix using dough hook: flours, starter, milk, sugar, water, and salt then allow to rest for 10 minutes.

Add the butter a piece at a time, mixing until fully incorporated before adding another piece. Once all butter has been incorporated, continue mixing on moderate speed with the dough hook for 5 minutes.

Begin with 3 stretch-and-folds in the bowl at 30 minute intervals at 30/60/90 minutes. After that, let the dough rest for the remainder of the bulk fermentation.

Keep dough bowl covered and in a warm place during this process.

(For my stretch-and-folds, sometimes I take the dough out of the bowl and work on the counter, more of the "slap and fold" technique and other times I use a curved edge bowl scraper and work in the bowl (faster that way), scooping the dough from bottom of bowl to top around the clock positions, noon, 3, 6, and 9.)

Sprinkle cornmeal onto a sheet pan. Scoop dough from the bowl onto counter, cut into 12 pieces, shape each into a taught ball, and transfer to prepared sheet pan. Cover with a piece of greased plastic wrap, set in a warm place, and let proof for 2 to 3 hours, until very puffy.

Preheat oven to 350ºF and line a sheet pan with parchment. Preheat griddle (or use a frying pan and cook in batches) and grease with unsalted butter. Gently transfer dough balls (as many as will fit without touching) to griddle, cook until brown on bottom, flip and cook the other side—3 minutes per side. Transfer to prepared sheet pan. Bake for 15 minutes.

Transfer to cooling rack and keep in a bread bag or freeze for longer storage. Fork-split is best before toasting! Enjoy