Preheat oven to 325F. Grease an 8" round baking pan.
In a large bowl stir together sugar, flour, cocoa, and salt. Mix in vanilla, butter, eggs, and 3/4 cup chopped nuts, if using, until combined and scrape into baking dish.
Wash your mixing bowl and place it in the freezer along with the beaters (for the whipped cream).
Bake 25-30 minutes or until a toothpick inserted removes with fudgy, rather than wet crumbs. While cooling, microwave fudge ice cream topping until it's thin enough to spread. Poke holes in warm pie and spread fudge over top. Cool completely.
In chilled bowl combine cream and powdered sugar. Whip to stiff peaks and spread over pie. Scatter remaining nuts over the top.