To start, dice a mild onion such as a shallot, leek or ciopollini and slice a large handful of mint leaves. Leaves such as mint and basil are easiest to cut if you chiffonade them by stacking the leaves on top of each other and rolling them lengthwise like a cigarette. From there they are easy to cut into thin strips.
Next chop the chard into 2×2 squares. Use some of the stems, but discard the really wide woody parts or save for your next stock. Stop cutting when there is no longer any green attached. When the stem gets thicker toward the bottom of the leaf, I recommend cutting them in half to ease cooking and eating.
Heat olive oil in a pan until it swirls easily. Add onion and some pistachio nuts and saute until the onion is soft and translucent (it’s okay if it starts to brown). Add chard and stir to cover in oil. Add salt, but not too much. Cover for 1-2 minutes and allow the chard to wilt. Uncover, stir and continue to cook. Sprinkle mint over the chard and stir. Salt and pepper to taste. Chard is finished cooking when it is dark green and the stems are tender, about 8 minutes.