To prepare the leeks with balsamic vinegar, begin by trimming the vegetables: cut off the root base and the dark, tough green tops. Wash the leeks thoroughly and cut them into fairly thick diagonal slices. Arrange them on a baking tray and cook in a steam oven for 10 to 15 minutes. Alternatively, you can cook them in a steamer basket; the key is not to let them become overly soft—they should remain slightly crisp.
Once cooked, transfer the leeks to a serving dish and dress them with a few drops of PGI balsamic vinegar and Maldon salt. If desired, finish with a light drizzle of extra virgin olive oil.