In a large bowl, combine the filtered water and active starter. Stir until mostly dissolved.

Add the salt and honey, mixing well until the honey is fully incorporated.

Add the white whole wheat flour and vital wheat gluten. Mix until a shaggy dough forms and no dry flour remains.

Cover the bowl and let the dough rest for 30 minutes.

After 30 minutes, wet your hands and perform one set of stretch and folds:

Pull one side of the dough up and fold it over the center. Rotate the bowl and repeat on all four sides.

Cover and rest 30 minutes.

Perform 3 more sets of coil folds every 30–45 minutes:

Slide your hands under the center of the dough, lift it up, and allow it to fold over itself. Rotate and repeat around the bowl.

The dough will become smoother and more elastic with each fold.

After the final fold, cover and let the dough bulk ferment at room temperature for about 5–7 hours, or until puffy with small bubbles and noticeably risen.

Lightly flour your counter and turn out the dough.

Gently flatten into a rectangle and remove any large air bubbles.

Fold both sides inward, then roll tightly into a loaf shape, tucking the ends under.

Place seam-side down into a well-buttered loaf pan.

Cover the pan and place in the refrigerator overnight (8–12 hours).

Preheat oven to 400°F.

Score the top of the loaf with a sharp knife or bread lame.

Bake for 30 minutes, or until golden brown and the internal temperature reaches about 200°F.

Remove from the pan immediately and cool completely on a wire rack before slicing.

Brush the top lightly with butter if desired.