How to Make It
In a large pot, over moderately high heat, heat the oil until shimmering. Add the chard and 1/2 teaspoon of salt and cook undisturbed for 20 seconds (the greens will brown a bit), then continue to cook, tossing occasionally with tongs, until wilted and just tender, about 3 minutes. Let stand off the heat for 30 seconds, then add the butter and toss until melted. Season with salt and serve.