Swiss chard is only one of three vegetables we recommend boiling to free up acids and allowing them to leach into the boiling water; this brings out a sweeter taste from the chard. Discard the boiling water after cooking; do not drink it or use it for stock because of its acid content.
Use a large pot (3 quart) with lots of water and bring to a rapid boil. Add chard to the boiling water. If stems are more than 1-inch wide, cook them for 2 minutes before adding the leaves. If less than 1 inch in width you can boil the leaves and stems together for 3 minutes. Begin timing as soon as you place the chard in the pot if you are using 1 pound or less of chard. If you are cooking large quantities of chard bring the water back to a boil before beginning timing the 3 minutes. Do not cover the pot when cooking chard. Leaving the pot uncovered helps to release more of the acids with the rising steam.
While we have not seen research on cooking, Swiss chard, and oxalates, there is some research on this topic with another chenopod family vegetable, spinach. Research has shown that the boiling of spinach in large amounts of water helps decrease the oxalic acid content by as much as 50%.
Dressing, and top with your favorite optional ingredients. For details see 3-Minute Swiss Chard.