Open the jars and drain the olives, putting them into a bowl. Pour in the gin, vermouth and chili oil and give them a stir. Leave to steep for half an hour or so while you get ready for your party.
You can put any leftover olives in a jar with a lid for another couple of days, or indeed longer though it's doubtful that will arise.
Ingredients
4 (8-ounce) jars pimento-stuffed green olives, this gives 4 cups