In Italian cookery terms, when you cook something “in fricassea”, it means that you add egg yolks that you have already mixed with lemon juice to a hot, cooked dish, at the very end, generally off the heat. The yolks thicken and become a velvety, lemony sauce that enrobe the other ingredients. The trick, obviously, is not to scramble them.It is a Northern Italian cookery technique that always delivers a subtle elegance to the final dish.
Typically, it is rabbit, veal, chicken and lamb, that are cooked “in fricassea” , the meat first being braised “in bianco”, without tomatoes. 
Some vegetables too can be cooked “in fricassea”: artichokes, peas, mushrooms, carrots, courgettes, broad beans and asparagus.