5 tablespoons unsalted butter
5 leeks, white and tender green parts only, halved lengthwise and thinly sliced crosswise on the bias
2 thyme sprigs
Kosher salt and freshly ground pepper
In a large skillet, melt the butter. Add the leeks and thyme sprigs and cook over moderately low heat, stirring occasionally, until the leeks are very tender, about 15 minutes. Discard the thyme sprigs. Season the leeks with salt and pepper and serve.