Putting a chametz spoon in a pot of cooking Passover soup. What happens to the soup and pot?
If the soup was 60 times the volume of the head of the spoon which you inserted into the soup, which is usually the case for a full pot of soup, the soup and pot remain kosher. This only applies to such a mishap taking place before Pesach.
Shulchan Aruch 447:4, Mishna Brura ibid. 21.