What happens if the butter is too cold in puffed pastry dough?

If butter gets too cold while you're making puff pastry dough, it can cause problems later on. When the butter is too cold, it's more difficult to incorporate it into the dough and it may end up in small lumps which won't combine correctly with the surrounding dough later. This can lead to a pastry that is flaky and uneven, with some parts being tough and others being soggy. The pastry may also be more prone to breaking during the rolling and folding process as it won't be as pliable as when the butter is correctly integrated into the dough.

To prevent this, make sure you bring the butter to the right consistency before using it. The butter should be cold but not hard. You should be able to easily press your finger into it without it crumbling but it shouldn't be so soft that it's gooey or sticky. If it is too cold, let it sit at room temperature for a few minutes before using it.