Recipe adapted from 'Whole Wheat Sandwich Bread' by Maurizio at The Perfect Loaf
Mix together the flours, barley malt, and 440 grams water (this might be sufficient and will keep your dough from being too wet; only add up to the remaining 15 grams if necessary). Cover the bowl with plastic wrap or a clean kitchen towel and let sit in a warm place for two hours. (I set my bowl on top of my radiator here in Montana).
To the "Dough Autolyse" add the levain and salt and mix together. (Sometimes I use the dough hook on my mixer, sometimes I fold it in by hand using a small bench scraper. I've found that the hand mixing makes for a more tender and open crumb in the final bread.) Cover the bowl and set in a warm place for 4 hours. Every 30 minutes do a series of folds to the dough with your small bench scraper—I scoop to bottom and fold it to the middle every 90° around the dough in the bowl, going around a couple times. Unthink everything you've ever learned about "kneading bread dough". With sourdough, these gentle folds are sufficient (and far superior) for developing the gluten structure. At the last fold, turn the dough out onto a clean work-surface and shape into a round using quick tucks with your bench scraper, dough will be jiggly and somewhat loose, just do your best. Let sit 20 minutes.
Spray a 9"x4" pullman-style or other loaf pan with non-stick spray or rub inside with a little olive oil.
Shape your loaf with a large, straight-edge dough scraper—aim to fold each edge to center then the 90° edges to center then flip it upside down into the pan. To neaten things, tuck edges in using your bench scraper moistened with water. Cover pan with plastic wrap. At this point you can pop it in the refrigerator overnight, but I like to give it a head start by letting it proof for a couple hours at room temperature before going into the refrigerator. In the morning, take the pan out of the refrigerator and let it proof at room temperature while you preheat the oven. You want the dough to come close to the top of the pan.
Preheat oven to 450°F with rack set in bottom third. Bake bread for 20 minutes, lower temp to 425°F and continue baking for an additional 25 - 30 minutes until golden brown and internal temperature hitting 200°F. Let cool in pan a few minutes, then transfer from the pan to a rack. Try not to cut into it for at least a couple hours, the longer you wait the better for the bread as it is still setting inside.