DAY ONE: Prepare the poolish by combining the first measure of water, yeast & bread flour together in a medium mixing bowl mixing by hand to a pasty dough
Cover & refrigerate for 2 hours then remove from the refrigerator & let it sit covered on the counter at room temperature overnight (8 - 10 hours) *I recommend to start this step in the evening timed with your schedule for the next day to proceed approximately 8-10 hours later in the morning DAY TWO: In a large mixing bowl combine the second measure of both bread & whole wheat flours with the yeast, sugar & salt.
With a box grater (or simply cut the butter up into tiny pieces) grate the butter into the flour to distribute it evenly through the flour mixture with your finger tips
Add the warm water & now the room temperature poolish dough from yesterday & combine everything together very well by hand
You can also use a stand mixer with a dough hook for this entire recipe if you prefer!
Knead the dough for 4 minutes then rest for 2 minutes, then knead for 2 more minutes
Place the dough into a lightly oiled bowl, cover & let rest for approximately 40 minutes to 1 hour or until it has almost doubled in size
Turn the dough out onto a lightly floured surface & gently fold it over onto itself several times, almost like you are folding a letter then let it rest on the table for 15 minutes
Meanwhile preheat the oven to 475°F & line a sheet pan with parchment paper
With a light dusting of cornmeal on the table to prevent sticking, roll the dough to approximately 12" x 12" rectangle & approximately 1/4" thickness
Cut the dough with either a 3½" cookie cutter for round muffins or slice through the dough evenly into 16 portions (4 X 4 through the entire dough) making each muffin approximately 3" x 3" square
Heat your skillet on the stove top & once it is very hot place as many muffins as you can fit & cook each one for 1 minute on each side then transfer them to the sheet pan
Once they are all cooked in the skillet and lined up on the sheet pan bake for the remaining time of approximately 6-8 minutes until golden browned (the internal temperature should be 200°F)
Remove from the oven & transfer to a wire rack to cool before fork splitting them and toasting them!