I coated the bottom of an 9x12 pan (I think) with colored mini marshmallows (after I sprayed it with Crisco). I didn't use the vanilla. I used an electric mixer to beat it, and even then it took a little while. I think the only way I would beat it by hand is if I had several helpers to take turns beating. I think I am going to beat it longer next time, because it wasn't very thick. I poured the fudge over the marshmallows.
But, everyone liked it, and there were only about 5 pieces left the next day!
But, let me warn you. Make sure you use a big enough pot because of the amount of milk in this recipe. You should probably use at least a 4 quart saucepan. I tried to make this recipe months ago, but I used to small of a pot and it boiled over and became a sticky mess.
3 cups of sugar
1 1/2 cups of milk
2/3 cup of cocoa
1/4 cup margarine or butter (1/2 stick)
1 tsp vanilla
Combine the milk, sugar and cocoa in a saucepan big enough so that the mixture does not boil over. Mix well to be sure all the cocoa is absorbed. Cook on high constantly stirring until it boils; then lower the temperature to medium. Cook until it reaches soft ball stage. Add the butter and vanilla. Do not stir. Allow to cool for 10 minutes or so, then stir, stir STIR until it gets thick and looks like wet cement. Immediately pour onto a buttered dish and chill.