How to undo a reconciliation?

How to undo a reconciliation?

I need to update the "Expense Account" field on a bunch of expenses that I've already reconciled.  However, the system will not allow this field the be changed since it is reconciled.  I haven't found a way to remove the reconciliation status for the update.  I'm also not able to delete the transaction and re-enter.

What are my options for updating the Expense Account entry for a reconciled transaction?