Heat the oil in a large pan. Sauté the vegetables in batches, return to the pan along with the shallots. Fill the pan with enough water to just cover the vegetables, bring to the boil. Reduce the heat, simmer uncovered for approx. 45 mins. Add a little more water to ensure that the vegetables remain just covered.
Line a large sieve with a cheesecloth, strain the stock. Don't squeeze out the vegetables otherwise the stock will become cloudy. Add the ginger to the stock along with all the other ingredients up to and including the pepper. Turn off the heat and leave the stock on the hob to infuse for approx. 15 mins., strain.