Melt chocolate and margarine in a double boiler and stir well. Add the sugar. Remove from heat and let cool slightly. Whisk in eggs one at a time. Stir well until slightly thickened. Add cake meal and salt. Mix in chocolate chips, marshmallows and walnuts. Pour batter into prepared baking pan. Bake for 30 minutes or until set.
Remove pan from oven and sprinkle with additional marshmallows. Return pan to oven and bake 3-4 minutes longer, just until marshmallows are puffed. Don't overbake.
Remove pan from oven. Melt the chocolate chips for the topping, and drizzle all over the brownies. Immediately sprinkle with ground walnuts, before chocolate has had a chance to cool and harden. To serve, cut into squares. These freeze well.