Transfer broth mixture to a large saucepan. Bring to boiling; reduce heat. Simmer, covered, for 5 minutes. Meanwhile, in a medium bowl, combine whipping cream, flour, and egg yolks. Gradually stir about 1 cup of the hot broth mixture into the egg yolk mixture, then return egg yolk mixture to the remaining hot broth mixture. Cook, stirring constantly, until mixture is thickened and bubbly. Stir in chopped poultry, mushrooms, yellow squash and artichokes. (The mixture will become more saucy after baking.) Divide the filling among six 14-ounce au gratin dishes or individual casseroles.