Simple vegetable stock

Of course you can use a packet stock, or another ready made option, but as what you really want is simply nicely flavoured liquid, this simple stock means that you can have it fresh, and without added ingredients you might not choose. I find most ready made stocks too salty, so always use a variation on this.
Add a chopped onion, some celery if you have some, some bay leaves, peppercorns, dried mushrooms, to some water and boil until the flavours are absorbed by the water. This doesn't take long and means that stock you can control is always nearby.