FILLING: In saucepan combine sugar, flour, and cocoa. Stir in 1/2 cup milk and butter; cook and stir until bubbly. Cook 1 minute more. Stir in vanilla. Set aside. Let cool.
Combine biscuit and 1/3 cup milk. Roll dough on a floured surface to 1/8" thickness, cut into 4" circles. Put 1 tablespoon of filling in center of circle. Fold over, press edges together with tines of fork.
In skillet, heat 1" cooking oil to 375 degrees. Fry pastries, several at one time 2 minutes per side or until golden brown. Sprinkle with powdered sugar.