Sauté the shallots in the olive oil gently for 4 minutes, making sure they don't colour. Cut the potatoes into small cubes. Add to the shallots and cook for a further 2 minutes.
Remove from the heat and add the flour, mixing well.
Cut the kernels of corn from all of the cobs and run a knife down the side of each kernel to extract the juice. Add to the pan along with the stock and bay leaf. Mix well, bring to the boil and simmer for 20 minutes.
Add the milk and ham, bring to the boil again and serve topped with chopped chives.