Youvarlakia with Mushrooms, Eggplant and Walnuts in Egg-and-Lemon Broth

Meatballs made with ground veal and rice, simmered in broth and finished with avgolemono (egg-and-lemon sauce), are a popular Greek comfort food—the kind of winter one-pot meal that both adults and children enjoy. My vegetarian youvarlakia look exactly like the dish my mother used to make, but they are made from completely different ingredients; they are inspired by Domenica Marchetti’s Eggplant and Porcini “Meatballs” in Tomato Sauce, an ingenious Sicilian recipe from her boo