Mix the dough & rest overnight: In medium bowl, stir together the all purpose flour, whole wheat flour, yeast and salt. Add the warm water and vinegar and stir with a wooden spoon or dough whisk until all flour is incorporated. Place the bowl in a proofing bag or cover with plastic wrap. Rest at room temperature overnight (12 to 18 hours). The resulting dough will be bubbly and very sticky.
Shape the dough: When ready to bake, remove the dough from the bowl onto a clean, lightly-floured countertop. Gently spread the dough into a square and then fold up each side into a packet. Flip the dough over. Place your hands behind the dough and gently pull the dough towards you to increase the tension on the surface of the dough. Rotate and repeat until you have a boule shape. Follow this video tutorial for boule shaping technique.
Proof the dough for 1 hour: Place the boule on a piece of parchment paper about twice the width of the boule. Cover the dough with an inverted large bowl and rest one hour.
Preheat the oven: Preheat the Dutch oven (with lid) at 475°F for 30 minutes. (Or for the pizza stone method, place the pizza stone on middle rack of oven, off to one side. Place a cast iron pan or thickest baking sheet on the rack just below and off to the other side of oven. You’ll pour water into it later to create steam.)
Score the bread: Use a sharp knife or lame to cut several shallow slits at angle across the top of the dough. The photographs show this cross pattern.
Bake for 16 minutes: Working quickly and carefully with oven gloves or mitts, transfer the dough on the parchment paper to the preheated Dutch oven, then place the top on. Bake for 16 minutes. (Or for the pizza stone method, transfer the dough on the parchment paper to the preheated pizza stone. After the bread is on the the stone, make the steam: cover your hand with a towel and very carefully pour 1 cup of water onto the cast-iron pan or baking sheet, then immediately close the door.
Reduce to 400°F and bake for 25 to 27 minutes: After the 16 minutes, reduce the oven temperature to 400°F. Remove the Dutch oven, carefully take out the bread, and set the bread directly onto the oven rack. (Or for the pizza stone method, open the oven door a couple of times to fan out excess moist air.) Bake for an additional 25 to 27 minutes, until hollow when tapped or internal temperature is at 205 to 209 Fahrenheit. Remove the bread from the oven and allow it to cool on a cooling rack for at least 45 minutes. After cooling, the bread is ready to eat. Store the bread wrapped in cloth or in a bread bag on the counter for up to 2 days, or freeze (sliced) wrapped in foil in a plastic bag for several months.