I made some chutney a few days ago, but after cooling, and even overnight in the refrigerator, it is still very runny. Should I empty the jars back in the pan and cook until it thickens more, or what?
Just drain some of the "juice" off by putting the mixture in a sieve over a bowl for half an hour or so, and store it separately. If the chutney dries up later, as it may do, you can add some "juice" to restore it.
Don't forget, don't use jars with metal lids over vinegar-mixtures or the vinegar will destroy the metal from inside.
You need to re-boil it as, unless the vinegar is sufficiently concentrated, the chutney won't store. The above answer is wrong as you won't be concentrating the vinegar. To avoid the vinegar eating into metal lids, just put a double layer of clingfilm over the jar before putting the lid on.