Fat, such as butter or chicken fat, for sautéing the vegetables and for providing richness. Dressings for chicken and turkey, which are lean, may require more fat than dressings for duck and goose, which are fatty.
Liquid, usually stock, to provide moisture.
Seasonings, herbs, and spices.
Eggs, sometimes added as a binder but not always necessary.
Other ingredients for flavor, character, and bulk, such as: