Combine in a heavy saucepan 2 Tbs cocoa (Hershey's appears to be
the preferred brand), about 2 Tbs sugar, more or less, depending
on how sweet you like it, and 1 Tbs flour. Mix thoroughly.
Into that mixture, add about 1 cup of milk, a little at a time,
mixing until smooth. If it ends up being too thick, you can add
more milk later to thin it.
Place the pan over medium heat and bring to a simmer, stirring
frequently, till thickened. Check for desired thickness and sweetness,
and adjust if necessary.
Remove from the heat, and stir in 1 tsp of vanilla extract.
Pour over buttered biscuits, and serve with cold milk. Makes about
one cup, which is two servings or so.