Add the room temperature water into a large bowl. Add the active starter to the water and stir until the starter is dissolved. Mix in bread flour, whole wheat flour, and salt into the bowl. Mix well until all bits of flour are moistened and have formed a soft tacky dough.
Cover with a damp towel and let rest for 20 minutes.
After letting the dough rest, knead the dough for an additional 4 to 5 minutes. You want a soft dough that’s somewhat tacky. You can either use your stand mixer with the dough hook or use your hands. I enjoy kneading the dough myself; it is a workout, and I love the feeling of the dough coming together! Note here, you also want a pretty wet tacky dough, but if your dough is too wet, you can also add more flour here. I would begin adding 1 tbsp at a time while kneading it.
Place the dough back into the bowl, cover with a damp kitchen towel, plate or plastic wrap and let your dough rise for 1 hour.
After an hour, turn the dough out onto a lightly floured surface. Fold it like a business letter. Then do a quarter turn and fold it again and once more. Place the dough back into the bowl and let it rise for 15 minutes, and do another letter turn, do this 2 more times, at 15 minute intervals, for a total of 4 folds. After the 4 folds, place the dough back into the bowl and let the dough rise for another 15 minutes.
After your last fold and 15 minute resting period, turn the dough out onto a floured surface. Gently shape it into a round by gently cupping the dough, pulling and twisting it towards you while building surface tension.
Place the rough back in the bowl and cover and let rise for another 20 minutes. Then place the covered bowl, recommend covering the bowl with a fitting lid or plastic wrap to prevent the fridge from drying out your dough, in the fridge and let it rise for 8 to 12 hours.
Remove the dough from the fridge, and let sit at room temperature for an hour. After an hour, do your final shaping of your bread. Repeat the letter folds and then gently shape it into a round, like you did before putting the dough in the fridge, by gently cupping the dough, pulling and twisting it towards you while building surface tension. Place the dough on parchment paper or a silicone baking mat with the seam side down. Let the dough rise for another 30 minutes.
While your dough is on its last 30 minutes rise, place your empty Dutch oven inside the oven and preheat to 450°F.
Score the bread using a bread lame, razor blade, or sharp knife, and make 2 deep diagonal slashes into the dough.
After your oven and Dutch oven have preheated, carry the dough by the corners of the parchment paper or silicone bread mat like a sling and very carefully place it into the preheated Dutch oven. Then place the lid back on the Dutch oven.
Bake your bread with the lid on for 35 to 40 minutes. Remove the lid and bake for an additional 10 to 15 minutes until the crust is golden brown.
After your bread has been baked, resist and let your bread fully cool before cutting into it. If you cut your bread while it is hot, it will ruin the structure of your bread.
Your Bread will keep for 5 to 6 days in a bread bag on the counter. Note that the bread can be sliced and placed in the freezer and will stay fresh for 3 to 4 months in the freezer.