A batch of Bay Area bakers are promoting freshly milled flour, the latest obsession in this local favorite.

The baker’s cuts allow the loaf to uniformly ‘pop’ inside the oven, resulting in a lighter more open interior.

There’s a certain history and lore when it comes to San Francisco and sourdough. Thomas “Mac” McConnell, owner of The Midwife and the Baker, has a theory—and it comes in waves.

The first is Boudin Bakery, founded in 1849, with a mother starter that’s more than a 150 years old. It’s how a tourist pictures sourdough: blistered, chewy, a bread bowl brimming with chowder. The second is Acme Bread, founded in 1983, homegrown in Berkeley, served at the Ferry Building and still on the menu at Chez Panisse, with a light, crisp and mild baguette. The third is Tartine, and given that you’re reading a sourdough story, you’re probably already a fan, but it’s worth saying again: Chad Robertson has inspired a global following, with a dramatically dark crust pushed to the brink of burning, and an airy, custardy crumb.

Now, the new wave of sourdough: freshly milled flour. That’s where McConnell and two other local bakers come in.

Walk into his old warehouse, with paint peeling off the walls, and you’ll be enveloped in a cloud of flour. It’s shimmering everywhere, on your hands, your hair, settling on every surface. An unmistakable scent fills the air, and a dude with a grin and a trucker hat hands you a dark and craggy loaf of bread. It smells like burnt honey. It’s still warm from the oven. Rip into the center, and the flavor is wild. McConnell isn’t just quietly putting out some of the most beautiful bread in the Bay—he’s also one of the bakers leading the movement in freshly milled flour. You might think of flour as a pantry staple, a white powder sitting in a bag on a shelf, ready to dip into whenever you’re craving cookies. But that type of flour only dates back to World War II, when factories started to take the whole grain, strip away the bran (its shell, which contains fiber and B vitamins) and germ (the embryo rich in B vitamins, E vitamins and healthy fats). The result was a highly processed product with less nutritional value, but easy to ship and store.

Cut loaf reveals the color gradient.

Wheat is a natural ingredient, filled with flavorful oils, but as soon as you crack it, those sweet and floral aromas begin to fade. For sourdough bakers, who already rely on natural leavening, it only makes sense to return to the most natural ingredient. It’s an epic commitment—milling your own grains requires a Herculean amount of time, effort and equipment. Josey Baker was the first to roll a stone into his bakery, at least in the city proper. When the Mill opened more than five years ago, many people didn’t realize there was literally a mill in the back, but they were hooked on the flavor. These were the loaves that inspired the cinnamon toast trend, and there’s still a long line out the door. “Oh, it’s a s--tload more work,” laughs Baker. Both he and McConnell are working with New American Stone Mills, which have granite discs ranging from 26 to 48 inches. They’re designed to spin slowly and stay cool to avoid heating those flavorful oils, and they’re cut with geometric furrows to break down every last grain.

By doing it themselves, local bakers get to work with local grains. They’re grinding their own flours daily; pushing higher percentages of whole wheat; and experimenting with heritage varieties, such as Kamut, emmer and einkorn. For Avery Ruzicka of Manresa Bread, it’s an opportunity to partner with small farms, such as Chico’s Rancho Llano Seco and Coke Farm in San Juan Bautista. Blanca Grande, a soft white wheat, comes out creamy in the levain. Patron, a hard red wheat, imparts earthiness to the 100% whole wheat. Yecora Rojo, another red variety, brings a touch of brightness to the baguette.

Thomas “Mac” McConnell, owner of The Midwife and the Baker

“You can try a dozen loaves of sourdough, and they could all be excellent,” Ruzicka says. “But the one made from freshly milled flour stands out. It’s not one note; it’s not just sour—it reaches fuller depths and dimensions of flavor.”

Conventional bread uses flour that’s months old, but the bread is made in a matter of hours. In contrast, artisan sourdough might be made with freshly milled flour, but it takes two to three days to fully ferment. The process is less predictable, and the challenge is consistency. When Manresa was building out and opening multiple locations, Ruzicka would sleep a couple hours in the van in order to perfectly time the entire process—milling, mixing, fermenting, shaping, proofing and baking. “Freshly milled flour introduces so many variables,” says Ruzicka, “You either have to do it completely yourself or really train and trust a tight team.”

There is a poetry to McConnell, who owns the biggest bakery with an in-house milling operation in the San Francisco Bay Area, working out of an old Acme warehouse, bringing the story of sourdough full circle. He’s milling more than 3,000 pounds of flour per week; putting out 6,500 loaves of bread; and shaping not just levain loaves, but also baguettes, brioche and croissants. He’s taking tradition and iterating one revolution further, pushing for the freshest flour in pursuit of the fullest flavor. The local grain movement is happening across the country, but California still captures hearts and appetites when it comes to sourdough. And it is remarkable that San Francisco has three talented bakers making the commitment to mill their own grains, with this trio of tastemakers who are working the grind.

“When you rake your fingers through freshly milled flour, it’s lofty and fluffy,” says McConnell. “As soon as you add water and starter, it comes to life, transforming bread into what it was always meant to be.”