Want to transform leeks? Braise them. As the stalks simmer, they get soft and silky and the oniony flavor mellows into a savory sweetness. They're great with chicken or fish, or chop them up and stir into scrambled eggs before cooking.
Cut off the dark green tops of the leeks (save them for stock), then halve the stalks lengthwise. Rinse under cool water, separating the layers to get rid of any dirt. Cut off the root end, then transfer with a skillet with the stock, butter, and tarragon. Bring to a boil over high, then turn the heat to medium and simmer, turning once, until the leeks are tender, about 10 minutes. Season with salt and pepper.