The cream goes through a really "thick" stage before the butter separates out. At that point, Lauren pours the butter and the whey over cheesecloth (or a thin diaper rag!) into a strainer. Here she is using the strainer in a double broiler set, allowing the whey to drain into the pan beneath the strainer.
Here the butter sits while the other batches are being made. Lauren just pours each batch into the same cheesecloth, as long as she has the room.
When she's done with the last batch, she gently squeezes as much whey as she can out of the butter.
Lauren then leaves the butter to sit in the cheesecloth up to a few hours, allowing any remaining whey to further drain out. This seems to make a difference in the amount of buteric acid that builds up as the butter ages. The buteric acid is the guilty party for making your butter smell rancid as it seeps to the outside surface over time. To further avoid this buildup, we rinse the butter with cold water occasionally and pat it dry.
Lauren stores the butter in an airtight container for the fridge.
Dear Lauren, Thank you for all the time you put into making our great butter. I think of you every time I pull it out of the fridge, and each time I pass up the butter in the grocery aisle. Love, Mom