Thoroughly rinse the chard stems. Trim their ends and remove any remaining leaves with a sharp knife. In a large saucepan, blanch the stems for one minute. Immediately drain the stems and rinse them with cold water to stop the cooking process.
Add all remaining ingredients to a small saucepan and bring to a boil. In the meantime, tightly pack the chard stems into a glass jar and set aside. Remove the saucepan from the heat and allow the brine to cool slightly, about one to two minutes. Pour the brine into the jar, being sure to cover the chard stems completely. Allow to cool to room temperature. Seal the jar with a tight fitting lid. When kept covered and chilled, the pickles will keep well for 1-2 weeks.