1. Peel and quarter potatoes, place in a saucepan and cover with cold water.
2. Add some salt, bring to the boil and let simmer for about 15 minutes or until tender. Drain the potatoes and return them to the saucepan. Return to stove on low heat for a few minutes to evaporate excess water, watching carefully. Remove from heat and keep warm.
3. Finely slice shallots and saute in olive oil until translucent. Add balsamic vinegar and stir over a low heat until evaporated and sticky. Season potatoes to taste. Warm milk and add to mixture, mashing potatoes with a wire masher or a potato ricer.
4. Fold Persian feta and caramelised shallots well through mixture and serve.