Combine the cocoa and sugar in a saucepan.
Blend in the boiling water.
Bring this mixture to an easy boil while you stir.
Add in chocolate chips and stir until melted.
Simmer and stir for about 2 minutes.
Stir in 3 1/2 cups of milk and heat until very hot, but do not boil!
Remove from heat and add vanilla.
Divide between 4 mugs.
Add the cream to the mugs of cocoa to cool it to drinking temperature.