Leek and Potato Soup Ingredients 2tablespoons butter 1 tablespoon olive oil 3 large leeks (white and pale green parts only), halved lengthwise, thinly sliced (about 4 1/2 cups) 2 large russet potatoes (about 18 ounces total), peeled, diced 5 cups chicken stock or canned low-salt broth 2 tablespoons chopped fresh chives Preparation Melt butter in…