There are few things as delicious as a slice of sourdough bread with a generous layer of almost-cold-butter. But making it is not quite as simple as the pleasure of a piece of bread—but because this kind of stuff excites me, I wanted to share just how awesome sourdough bread is.

Sponge-Worthy Starter

What makes sourdough sour is the starter. Making the starter is the process of collecting wild yeast from the air using only flour and water. This is used for the sponge (the step before dough is actually formed). Over time it ferments and enough yeast is collected so that you don’t have to add dry yeast, active yeast or instant yeast to make your bread. As a bonus, the fermentation adds the distinct sour flavor. The thing that’s really amazing about sourdough starter is you can keep the same starter for a very long time as long as you keep feeding it. The bakery responsible for sourdough’s fame is Boudin Bakery. Not only did it make sourdough famous, but it also claims to be San Francisco’s oldest continuously running company. It has been using the same starter since the mid-1800s and refers to it as the “mother” dough. According to the bakery, the mother dough was even saved from the Great Earthquake of 1906 — it’s well-protected and well-preserved.