For the rice: Soak rice in water overnight. Drain and rinse thoroughly. Combine rice, dried mushrooms, and chicken broth in a rice cooker or 2-quart saucepan with a tight-fitting lid. Heat to boiling, reduce to a simmer, and cook for about 45-60 minutes, adding additional water or broth if needed. Continue cooking until the rice has puffed and split open, but is not overcooked and mushy. Fluff grains with a fork, and refrigerate until ready to make the stuffing. May be done several days ahead, and refrigerated.
For the stuffing: Heat fat in a medium saute pan until melted. Add onions, garlic, herbs, salt and pepper to taste, and mushrooms. Saute for about 15 minutes, stirring frequently. Combine with the cooled rice and serve with Thanksgiving turkey, or freeze in individual portions to serve as a side dish.