Tip the shallots into a large bowl, pour over a kettleful of boiling water, leave to stand for a minute, then drain. When cool enough to handle, sit down, turn the radio on and get peeling. Set the peeled shallots aside and place all the other ingredients except the balsamic vinegar into a large saucepan. Bring to the boil, lower the heat, then simmer for 3 mins. Drop the shallots into the pan and simmer for 8-10 mins until just tender. Use a slotted spoon to scoop the shallots and basil out into sterilised jars (see Know-how, below), then boil the liquid vigorously for 5 mins. Turn the heat off, stir in the balsamic vinegar, then pour over the shallots to cover. Seal the jars and leave for at least 3 days. Will keep for up to 3 months.