Although it's better known as a soup, avgolemono, the familiar Greek mixture of chicken broth, egg yolks and lemon juice, is also often used as a sauce. This quick vegetable braise of artichoke bottoms, carrots and potatoes, perfect for the season, is finished with a dill-enlivened avgolemono sauce. Made without the traditional chicken stock, it's a great vegetarian main dish served with Greek olives, feta cheese and a rustic bread, or as a side with grilled fish or lamb.It's easy to make…