Combine eggs, sugar, flour and vanilla extract. Melt margarine and add cocoa. Add to egg mixture and beat well. Add nuts. Bake in a 13 x 9-inch pan at 350 degrees F for 25 to 30 minutes.
As soon as cake is taken from oven, cover with marshmallows. Return pan to oven until marshmallows are slightly melted. Pour Chocolate Frosting over marshmallows and cool before cutting. Makes 48 brownies.