Hot Fudge Sundae Sauce

This is an oh-so-delicious chocolate sauce that I LOVED while growing up. The trick to this recipe is to make it only when you have a lot of people coming over, or when you can give most of it away. Otherwise, you end up eating most of it yourself.
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2 cups white sugar
4 Tbsp flour
4 Tbsp baking cocoa
1 can Evaporated Milk
1 stick butter
1 tsp vanilla
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 Mix the sugar, flour, and cocoa together in a saucepan, then add the evaporated milk and butter. Bring to a boil, stirring frequently, and let boil for 5 minutes. Remove from heat, add the vanilla, and let cool.

Serve over ice cream of your choice.