Combine 1000g white-bread flour and 1000g whole-wheat flour for the starter.

Mix 100g warm water (80 degrees) with 100g of the flour mix in a jar.

Mix until a thick batter consistency is achieved.

Cover with a towel and let sit at room temperature for 2-3 days, until bubbling occurs.

When starter shows activity, begin regular feedings.

Daily, discard 80% of the starter and feed the remainder with 50g warm water and 50g white-wheat flour mix.

Wait for the starter to predictably rise and fall with a sour smell (approximately 1 week).

Reserve the remaining flour mix for the leaven.

The night before baking, discard all but 1 tablespoon of the mature starter.

Mix the remaining starter with 200g warm water.

Add 200g of the white-wheat flour mix and combine.

Cover and let rest at room temperature for 12 hours until aerated and puffed.

Test leaven readiness by dropping a tablespoon into room-temperature water; it should float.

If it sinks, allow more time to ferment.

In a large bowl, combine 200g of leaven with 700g warm water.

Reserve remaining leaven for future loaves.

Add 900g white-bread flour and 100g whole-wheat flour, mixing until no dry flour remains.

Let dough rest for 25-40 minutes at room temperature.

Add 20g fine sea salt and 50g warm water.

Integrate salt and water into the dough thoroughly.

Cover the dough and transfer to a warm environment (75-80 degrees).

Let dough rise for 30 minutes.

Fold dough every half-hour for 2 1/2 hours more (3 hours total).

The dough should be billowy and increase in volume by 20-30%. If not, continue rising and folding.

Transfer dough to a floured work surface.

Cut dough into 2 equal pieces and flip so floured sides are face down.

Fold the cut side of each piece up onto itself, ensuring flour remains on the outside.

Work dough into taut rounds.

Place rounds on a work surface, cover with a towel, and let rest for 30 minutes.

Mix 100g whole-wheat flour and 100g rice flour.

Line two bread-proofing baskets or mixing bowls with floured towels.

Dust rounds with whole-wheat flour.

Flip them over onto a work surface so floured sides are facing down.

Take one round, and fold the bottom corners up into the middle third of the dough.

Repeat on the right and left sides.

Fold the top corners down over previous folds.

Roll dough over so the folded side becomes the bottom of the loaf.

Shape into a smooth, taut ball.

Repeat with the other round.

Transfer rounds, seam-side up, to prepared baskets.

Cover and return to the 75- to 80-degree environment for 3-4 hours.

Alternatively, let dough rise for 10-12 hours in the refrigerator, then bring back to room temperature before baking.

Preheat a Dutch oven or lidded cast-iron pot in the oven to 500 degrees (about 30 minutes before baking).

Dust tops of dough with whole-wheat/rice-flour mixture.

Carefully remove heated pot from oven and gently turn 1 loaf into the pan, seam-side down.

Score the top of the bread with a lame or razor blade.

Cover and transfer to oven.

Reduce temperature to 450 degrees and cook for 20 minutes.

Carefully remove lid and cook for 20 more minutes, until crust is a rich, golden brown.

Transfer bread to a wire rack to cool for at least 15 minutes before slicing.

Increase oven temperature to 500 degrees and repeat with the second loaf.