How to Make It
Combine the pesto and 2 tablespoons of the oil in a small bowl; set aside.
Heat the remaining 2 tablespoons of oil in a large skillet over medium-high heat. Add the chard stems, ¼ teaspoon salt, and ½ teaspoon pepper. Cook, stirring occasionally, until tender, 6 to 8 minutes. Add as many of the chard leaves as will fit and cook, tossing frequently and adding more leaves as there is room, until tender, 2 to 4 minutes.
Drizzle the chard with the thinned pesto. Serve warm or at room temperature.