Whisk together milk, eggs, sugar, yeast, and salt in a 6-quart bowl, or a lidded (not airtight) food container.
Whisk together all-purpose flour and potato flour in a bowl. Using a dough whisk or a heavy-duty stand mixer with paddle attachment, combine flours, butter, and milk mixture without kneading.
Cover (not airtight); allow to rest at room temperature for 2 hours, then refrigerate.
The dough can be used as soon as it’s thoroughly chilled, about 4 hours. Refrigerate the container and use over the next 5 days. Or freeze the dough in 1-pound packets for up to 3 weeks.