In a large mixing bowl, coarsely crumble dry toast.
Set aside.
In a frying pan, sauté onion, celery, and mushroom in 6 Tablespoons margarine until tender.
Mix in salt and black pepper.
Pour over toast. crumbs
Add 3 cups turkey stock, and mix together.
Let stand for about 10 minutes.
Toss well and pour into a greased baking dish.
Place turkey cubes on top of the dressing.
Melt 2 Tablespoons margarine.
Blend in flour and stir until bubbly.
Add 2 cups of turkey stock and milk. Stir briskly until it thickens.
Pour over turkey and dressing.
Drizzle on melted margarine.
Sprinkle breadcrumbs on top.
Bake in oven at 350° F for 1 1/2 hours.
Serve hot.